extractor: drop Latin-1 mojibake on Type0/CID fonts; tokenize wide TSR items (#75)

* extractor: drop Latin-1 mojibake on Type0/CID fonts; tokenize wide TSR items

Two text-extraction failure modes surfaced by table-candidate shadow
data; both also affect the existing TableFormer / vector-grid paths
since they share `extract_tables_with_structure_*_mem`'s downstream
cell-fill.

1. CJK / multi-byte mojibake. The bottom Latin-1 fallback in
   `extract_text_from_operand` ran unconditionally. For a Type0/CID
   (Identity-H) font whose ToUnicode CMap fails to parse, the bytes
   are CIDs (font-internal indices), not character codes — per-byte
   Latin-1 produces mojibake (e.g. 2-byte CID 0xCDD9 surfaces as "ÍÙ").
   Gate that fallback on `FontWidthInfo.is_cid` (set by
   `parse_type0_widths` for `/Subtype /Type0`). For Type0 fonts with
   any non-ASCII byte, emit one U+FFFD per CID instead so
   `detect_encoding_issues` still trips and the page is flagged for
   OCR — preserving the existing OCR-routing path that the
   high-Latin-1 garbage used to satisfy by accident. Type1 / TrueType
   simple fonts retain the per-byte Latin-1 round-trip (it IS the
   canonical interpretation for them; verified against an existing
   pdf-evals fixture where bytes like 0xB6 are legitimate Latin-1).

   Threaded `font_widths: &PageFontWidths` through
   `extract_text_from_operand` and its 5 call sites in
   `content_stream.rs` / `xobjects.rs`.

2. Dense-cell text collapse in `extract_tables_with_structure_cells_mem`.
   Stage-1 routing did per-item assignment — each TextItem went into the
   single cell whose bbox contained its center. When a row's text is
   rendered as one wide Tj (e.g. "Marshall Islands 0.9 0.9 0.9"), the
   whole row parks in one cell and the rest of the row stays empty.

   New `split_item_into_token_subitems` helper splits each item into
   per-token virtual sub-items with x positions estimated from
   `effective_width / char_count` and the token's character offset.
   Stage 1 then routes per-token. Single-token items collapse to a
   one-element vector (no behavior change). Multi-token items spanning
   multiple cells distribute correctly. Stage-2 orphan recovery now
   operates on token-grain orphans rather than re-trying whole items.

Tests:
 - `cid_font_with_unparseable_cmap_does_not_emit_latin1_mojibake` (unit)
   exercises the Type0/CID + unparseable-CMap fallback path.
 - `simple_font_latin1_fallback_passes_high_bytes_through` (unit)
   guards the false-positive case where a Type1 font's `/ToUnicode`
   reference is set but bytes are legitimate Latin-1 character codes.
 - `test_extract_tables_with_structure_distributes_wide_item_across_cells`
   (integration) builds a synthetic PDF with one wide Tj and asserts
   each token lands in its own cell.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* tests: pin CID mojibake fix mechanism with FFFD assertions

Two complementary tests for the Type0/CID Latin-1-fallback guard:

1. Tighten `test_identity_h_no_tounicode_suppresses_garbage` on the
   existing real-PDF fixture `shinagawa_identity_h.pdf` to also assert
   the pre-suppression text contains U+FFFD and contains no high-Latin-1
   chars. Pins down WHICH mechanism is suppressing the garbage so a
   future regression that re-enables Latin-1 mojibake fails loudly here
   instead of silently switching the suppression chain back to
   `is_cid_garbage` + high-Latin-1 detection.

2. Add `test_synthetic_type0_broken_tounicode_emits_fffd_not_latin1_mojibake`
   with a fully-synthetic Type0 / Identity-H PDF built in process. We
   control the malformed ToUnicode contents, the descendant CIDFontType2
   shape (just enough for `parse_type0_widths` to set `is_cid=true`,
   which is what the new guard keys off of), and the Tj byte stream.
   No fixture file or external license needed. Reproduces the exact
   "Type0 + non-ASCII bytes + unparseable ToUnicode" code path that
   produced the production mojibake samples.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/extractor/content_stream.rs

@@ -385,6 +385,7 @@ pub(crate) fn extract_page_text_items(
                         &font_encodings,
                         &encoding_cache,
                         &mut cmap_decisions,
+                        &font_widths,
                     ) {
                         let combined = multiply_matrices(&text_matrix, &ctm);
                         let rendered_size = effective_font_size(current_font_size, &combined);
@@ -533,6 +534,7 @@ pub(crate) fn extract_page_text_items(
                                     &font_encodings,
                                     &encoding_cache,
                                     &mut cmap_decisions,
+                                    &font_widths,
                                 ) {
                                     current_text.push_str(&text);
                                 }
@@ -620,6 +622,7 @@ pub(crate) fn extract_page_text_items(
                         &font_encodings,
                         &encoding_cache,
                         &mut cmap_decisions,
+                        &font_widths,
                     ) {
                         if !text.trim().is_empty() {
                             let combined = multiply_matrices(&text_matrix, &ctm);

src/extractor/fonts.rs

@@ -720,7 +720,11 @@ pub(crate) fn extract_text_from_operand(
     font_encodings: &PageFontEncodings,
     encoding_cache: &HashMap<String, Encoding<'_>>,
     cmap_decisions: &mut CMapDecisionCache,
+    font_widths: &PageFontWidths,
 ) -> Option<String> {
+    let is_type0_cid_font = font_widths
+        .get(current_font)
+        .is_some_and(|info| info.is_cid);
     let result = (|| -> Option<String> {
         if let Object::String(bytes, _) = obj {
             let mut decode_with_entry = |entry: &crate::tounicode::CMapEntry| -> Option<String> {
@@ -962,7 +966,31 @@ pub(crate) fn extract_text_from_operand(
                 return Some(symbol_text);
             }
 
-            // Latin-1 fallback
+            // Latin-1 fallback. Safe ONLY for fonts that use single-byte
+            // encodings — for these, an unmapped byte is a valid character
+            // code in Latin-1/WinAnsi space. CID fonts (Type0 / Identity-H)
+            // emit multi-byte CIDs that aren't characters; per-byte Latin-1
+            // produces mojibake (e.g. 2-byte CID 0xCDD9 → "ÍÙ" for the
+            // production scrape_id 019de78c-... samples).
+            //
+            // For a CID font (has_cmap is set OR a /ToUnicode reference
+            // exists) with any non-ASCII bytes, emit a single U+FFFD per
+            // CID instead. This both replaces the mojibake with a proper
+            // "decode failed" marker AND keeps `detect_encoding_issues`
+            // tripping so the page is flagged for OCR — the existing
+            // garbage-detection path that the high-Latin-1 mojibake used
+            // to satisfy by accident.
+            if is_type0_cid_font && bytes.iter().any(|&b| b > 0x7F) {
+                // 2-byte CIDs (Identity-H) are by far the common case; for
+                // an odd byte count we still emit at least one marker so
+                // detection downstream fires.
+                let cid_count = (bytes.len() / 2).max(1);
+                return Some("\u{FFFD}".repeat(cid_count));
+            }
+            // Pure ASCII bytes round-trip safely (Latin-1 == ASCII for
+            // 0x00..=0x7F), and non-CID (Type1 / TrueType / Type3) fonts
+            // use single-byte encodings where Latin-1 fallback is the
+            // canonical interpretation.
             Some(bytes.iter().map(|&b| b as char).collect())
         } else {
             None
@@ -1213,4 +1241,97 @@ mod tests {
         let bad = "###!!!@@@$$$";
         assert!(score_text(good) > score_text(bad));
     }
+
+    #[test]
+    fn cid_font_with_unparseable_cmap_does_not_emit_latin1_mojibake() {
+        // Type0/CID font (font_widths reports `is_cid=true`) where the
+        // ToUnicode CMap couldn't be parsed (FontCMaps doesn't have the
+        // obj_num). Bytes are a 2-byte CID stream containing high bytes
+        // that aren't valid UTF-8 — exactly the case in the production
+        // samples (Identity-H text where the ToUnicode CMap was missing
+        // or malformed, scrape_id 019de78c-..., e.g. "Í Ù Z)¿").
+        //
+        // Without the guard, the function falls through to the byte-by-byte
+        // Latin-1 fallback and produces "ÍÙ" (U+00CD U+00D9). The correct
+        // behavior is to emit U+FFFD per CID so downstream
+        // `detect_encoding_issues` flags the page for OCR.
+        let bytes = vec![0xCD_u8, 0xD9, 0xCD, 0xD9];
+        let obj = Object::String(bytes, lopdf::StringFormat::Hexadecimal);
+
+        let font_cmaps = FontCMaps::default();
+        let mut font_tounicode_refs: HashMap<String, u32> = HashMap::new();
+        font_tounicode_refs.insert("F0".to_string(), 999);
+        let inline_cmaps = HashMap::new();
+        let font_encodings: PageFontEncodings = HashMap::new();
+        let encoding_cache: HashMap<String, Encoding<'_>> = HashMap::new();
+        let mut decisions = CMapDecisionCache::new();
+        let mut font_widths: PageFontWidths = HashMap::new();
+        font_widths.insert("F0".to_string(), make_font_info(&[], 1000, true));
+
+        let result = extract_text_from_operand(
+            &obj,
+            "F0",
+            None,
+            &font_cmaps,
+            &font_tounicode_refs,
+            &inline_cmaps,
+            &font_encodings,
+            &encoding_cache,
+            &mut decisions,
+            &font_widths,
+        );
+
+        let text = result.expect("CID font fallback should still emit a marker");
+        assert!(
+            !text.contains('\u{00CD}') && !text.contains('\u{00D9}'),
+            "CID font with unparseable CMap leaked Latin-1 mojibake: {text:?}"
+        );
+        assert!(
+            text.contains('\u{FFFD}'),
+            "CID font with unparseable CMap should emit U+FFFD so detect_encoding_issues fires: {text:?}"
+        );
+    }
+
+    #[test]
+    fn simple_font_latin1_fallback_passes_high_bytes_through() {
+        // A Type1/TrueType simple font (is_cid=false) with a `/ToUnicode`
+        // reference but no usable CMap and no `/Differences` map.
+        // Per-byte Latin-1 IS the canonical interpretation here — these
+        // bytes are character codes, not CIDs. The CID guard must NOT
+        // strip them. Reproduces the false positive that an earlier
+        // version of the guard introduced for fonts in PDFs like
+        // pdf-evals/Navigating-Artificial-Intelligence-..., where bytes
+        // like 0xB6 are legitimate Latin-1 character codes.
+        let bytes = vec![0x24_u8, 0x47, 0xB6, 0x56]; // "$G¶V"
+        let obj = Object::String(bytes, lopdf::StringFormat::Hexadecimal);
+
+        let font_cmaps = FontCMaps::default();
+        let mut font_tounicode_refs: HashMap<String, u32> = HashMap::new();
+        font_tounicode_refs.insert("F1".to_string(), 999);
+        let inline_cmaps = HashMap::new();
+        let font_encodings: PageFontEncodings = HashMap::new();
+        let encoding_cache: HashMap<String, Encoding<'_>> = HashMap::new();
+        let mut decisions = CMapDecisionCache::new();
+        let mut font_widths: PageFontWidths = HashMap::new();
+        font_widths.insert("F1".to_string(), make_font_info(&[], 1000, false));
+
+        let text = extract_text_from_operand(
+            &obj,
+            "F1",
+            None,
+            &font_cmaps,
+            &font_tounicode_refs,
+            &inline_cmaps,
+            &font_encodings,
+            &encoding_cache,
+            &mut decisions,
+            &font_widths,
+        )
+        .expect("simple font should round-trip Latin-1 bytes");
+        assert_eq!(text, "$G\u{00B6}V");
+        assert!(
+            !text.contains('\u{FFFD}'),
+            "simple font fallback must not stamp FFFD over legitimate bytes: {text:?}"
+        );
+    }
 }

src/extractor/xobjects.rs

@@ -373,6 +373,7 @@ fn extract_form_xobject_text_inner(
                         &font_encodings,
                         &encoding_cache,
                         cmap_decisions,
+                        &font_widths,
                     ) {
                         let combined = multiply_matrices(&text_matrix, &ctm);
                         let rendered_size = effective_font_size(current_font_size, &combined);
@@ -517,6 +518,7 @@ fn extract_form_xobject_text_inner(
                                     &font_encodings,
                                     &encoding_cache,
                                     cmap_decisions,
+                                    &font_widths,
                                 ) {
                                     current_text.push_str(&text);
                                 }