feat: expose per-page markdown extraction to Python and Node (#53)

* feat: expose per-page markdown extraction to Python and Node (#49)

Implements the feature requested in issue #49: a list-of-pages markdown output
from the Python API. Matching the existing project pattern, the feature lives
in the Rust core and is surfaced through every binding.

- Rust core: `extract_pages_markdown` (path) and `extract_pages_markdown_mem`
  (bytes) now take `Option<&[u32]>` — `None` returns every page in document
  order; a slice restricts and preserves caller order.
- Python: new `extract_pages_markdown(path, pages=None)` and
  `extract_pages_markdown_bytes(data, pages=None)` functions plus
  `PageMarkdown` / `PagesExtractionResult` classes; stub file updated.
- Node: `extractPagesMarkdown(buffer, pages?)` — `pages` is now optional.
- Tests: 2 new Rust integration tests, 9 new Python tests, 2 new Node
  assertions. All 372 unit + 107 integration + 53 Python tests pass.

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

* chore: bump version from 1.3.0 to 1.4.0

Minor bump for the new per-page markdown extraction API exposed through
the Python and Node bindings.

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

---------

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

napi/src/lib.rs

@@ -343,21 +343,26 @@ pub struct PagesExtractionResult {
     pub is_complex: bool,
 }
 
-/// Extract formatted markdown for specific pages of a PDF, with layout
-/// classification metadata.
+/// Extract formatted markdown for pages of a PDF, with layout classification
+/// metadata.
 ///
 /// Returns per-page markdown and classification data (tables, columns,
 /// OCR needs) from a single parse. Font statistics are computed from the
 /// full document so header detection is consistent across pages.
+///
+/// Omit `pages` (or pass `undefined`) to return every page in document
+/// order. Pass an array of 0-indexed page numbers to restrict output to
+/// those pages, in caller-supplied order.
 #[napi]
 pub fn extract_pages_markdown(
     buffer: Buffer,
-    pages: Vec<u32>,
+    pages: Option<Vec<u32>>,
 ) -> Result<PagesExtractionResult> {
     let bytes: Vec<u8> = buffer.to_vec();
     catch_panic("extract_pages_markdown", move || {
-        let result = pdf_inspector::extract_pages_markdown_mem(&bytes, &pages)
-            .map_err(|e| to_napi_err(e, "extract_pages_markdown"))?;
+        let result =
+            pdf_inspector::extract_pages_markdown_mem(&bytes, pages.as_deref())
+                .map_err(|e| to_napi_err(e, "extract_pages_markdown"))?;
         Ok(PagesExtractionResult {
             pages: result
                 .pages