extract_tables_in_regions: needs_ocr on suspicious table structure (0.4.1)

When the heuristic returns markdown that looks like a partial / mis-detected
table, set needs_ocr=true so the caller falls back to GPU OCR. Previously the
same cases returned the broken table with needs_ocr=false, which produced
real-world TEDS=0 scores in fire-pdf evals (heuristic-built table didn't
match ground truth structure at all, but caller had no signal to fall back).

Four failure modes detected, all observed in opendataloader-bench eval losses:

1. **Header looks like a data row** — first cell of header is a bare number
   (e.g. `|2|...`), suggesting the actual header row was skipped. Real
   headers almost never start with just a number.

2. **Empty header cells in a multi-column table** — ≥3 cols, ≥1 empty cell
   in the header row. Indicates poor column boundary detection.

3. **Duplicate header cells** — same non-empty value appearing twice in the
   header (e.g. "Administration|Administration"). Means a multi-line header
   was collapsed wrong.

4. **Sparse first data row** — ≥3 cols and ≥1/3 of first-data-row cells are
   empty. Multi-row headers in the source PDF get smashed into header +
   sparse data row by the heuristic; this catches that.

Tests: 9 new unit tests in `looks_like_partial_table_tests` cover each
failure mode plus realistic non-failures (well-formed table, single-column
list, two-col with a single empty cell). All 91 existing tests still pass.

Bumps `napi/package.json` to 0.4.1 since this changes the function's return
behaviour for callers (some inputs that returned needs_ocr=false now return
true). The output text field is also cleared on the new fallback path so
callers don't accidentally use the broken markdown.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

napi/package.json

@@ -1,6 +1,6 @@
 {
   "name": "firecrawl-pdf-inspector",
-  "version": "0.4.0",
+  "version": "0.4.1",
   "description": "Fast PDF classification and text extraction. Detect text-based vs scanned PDFs, extract text by region with quality checks. Native Rust performance via napi-rs.",
   "main": "index.js",
   "types": "index.d.ts",