fix(metadata): detect sectPr nested in tables; ignore text-box sections (#51)

[JSv4]

Summary

Closes #51.

WmlToHtmlConverter.GetDocumentMetadata() reported the wrong number of sections for documents whose section break lives inside a table cell. CollectSectionData scanned only the body's direct children:

var blockElements = body.Elements()
    .Where(e => e.Name == W.p || e.Name == W.tbl || e.Name == W.sectPr)
    .ToList();

so a w:sectPr carried by a paragraph nested in w:tbl/w:tr/w:tc/w:p/w:pPr was invisible. Such a document reported one section instead of two, and the per-section page dimensions and paragraph/table index ranges used for lazy-loading pagination were wrong. The method even carried a comment flagging this as a known limitation tracked by this issue.

This is the Document Metadata API in WmlToHtmlConverter.cs — it is not part of redlining, WmlComparer, or the DocxDiff engine, so no comparison code is touched.

The fix

CollectSectionData now walks the body as a single main story in document order:

• It descends into tables (w:tbl → w:tr → w:tc) because a cell's content is part of the main story, so an in-cell section break is detected and attributed to the section it starts in.
• Each w:p is treated as a leaf — only its direct w:pPr/w:sectPr is inspected, never its runs. Because a text box (w:txbxContent) is always nested inside a run, a w:sectPr inside a text box is excluded automatically, along with text-box paragraphs. A text box is a separate story that does not paginate the main document; counting its section properties would invent a phantom section and corrupt the metadata. Headers/footers/footnotes/endnotes/comments live in their own parts and are out of the body tree by construction.
• Only body-level tables count toward the table total (a nested table is part of its containing cell's content), preserving the pre-fix counts for the common case.

w:sectPr placement	Counts as a main-document section?
w:body/w:p/w:pPr/w:sectPr (body paragraph)	✅ (unchanged)
w:body/w:sectPr (trailing/final)	✅ (unchanged)
w:tbl/w:tr/w:tc/w:p/w:pPr/w:sectPr (table cell)	✅ new
…/w:txbxContent/…/w:sectPr (text box)	❌ separate story

The change is self-contained: CollectSectionData has exactly one caller (GetDocumentMetadata), and the public DocumentMetadata/SectionMetadata shape is unchanged, so the WASM/npm surfaces pick this up with no wire change.

Testing

• New regression tests in DocumentMetadataTests.cs:
  • DM022_GetDocumentMetadata_DetectsSectionBreakInsideTableCell — an in-cell break now yields 2 sections, the table is attributed to the section it starts in, and paragraph/section indices stay contiguous.
  • DM023_GetDocumentMetadata_IgnoresSectionPropertiesInsideTextBox — a text-box w:sectPr does not create a section (single section, governed by the body w:sectPr), and text-box paragraphs are not counted.
• Full suite: 2671 passed, 3 skipped, 0 failed (dotnet test).
• Release build (-c Release, TreatWarningsAsErrors=true) is clean — no new warnings from the changed file.

Docs

• CHANGELOG.md — entry under [Unreleased] → Fixed.
• docs/ooxml_corner_cases.md — new section documenting why a table-cell w:sectPr is a section break while a text-box w:sectPr is not (separate-story rule).

🤖 Generated with Claude Code

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