fix: resolve DOCX table style cell margins

[developer0hye]

File submission policy

• Any submitted sample files or attachments satisfy the submission policy, or none are submitted.

Summary

Resolved DOCX table-style cell margins are now complete. A style named “Normal Table” uses Word’s latent 0/108/0/108 twip margins when its own margin declaration is absent or partial. Other resolved styles preserve declared sides and inherit unspecified sides from the default table style, or use zero when that default supplies no value. Direct table and per-cell margin precedence remains unchanged.

Four generated DOCX probes cover absent and one-sided style margins under both “Normal Table” and “Grid Probe” names. The style IDs deliberately differ from the names so the regression verifies Word’s name-based built-in resolution.

Related issue

Related: #1884
Related: #1874

Testing

• cargo fmt --all -- --check and git diff --check passed.
• cargo test --locked --workspace --profile ci passed after integrating main 71e10311; a fresh --doc run also passed after the separate CLI build.
• cargo clippy --locked --workspace --all-targets -- -D warnings passed.
• Four fresh native Word probes passed layout, normalized text and strict cluster audits.

Visual impact

• No rendered PDF change
• Rendered PDF change or visual evidence added

Visual audit

• Issue: DOCX: a default table style that states no or partial w:tblCellMar still falls through to Typst's 5pt cell inset #1884
• Fixture: tests/fixtures/docx/issue-1884-normal-absent.docx, tests/fixtures/docx/issue-1884-normal-partial.docx, tests/fixtures/docx/issue-1884-custom-absent.docx, tests/fixtures/docx/issue-1884-custom-partial.docx
• Page(s): 1-4
• Renderer and DPI: pdftoppm, 150 DPI
• Evidence mode: fix
• Layout audit report: assets/bugfixes/issue-1884/layout-audit.json
• Render cluster reports: assets/bugfixes/issue-1884/render-clusters-page-1.json, assets/bugfixes/issue-1884/render-clusters-page-2.json, assets/bugfixes/issue-1884/render-clusters-page-3.json, assets/bugfixes/issue-1884/render-clusters-page-4.json
• Reference exporter differences: None
• Fine-detail threshold: 1pt
• Layout audit page count: Pass
• Layout audit text flow: Pass
• Layout audit visible fills: Pass
• Layout audit rectangle geometry: Pass
• Layout audit large shifts: Pass
• Layout audit fine shifts: Pass
• New follow-up issues found in this audit: None
• Model vision findings: Full pages, diffs and matched content crops show both cells and the following paragraph in the native positions. The custom partial style's explicit top inset remains visible; absent sides no longer introduce Typst's unrelated 5pt inset. No missing text, wrap, clipping, overlap, rotation, fill, rule, or emphasis discrepancy was observed. These probes contain no painted borders, hairlines, pictures, bold, italic, or underlined runs. Sub-material cell-text anchor offsets are at most 0.22pt horizontally and 0.167pt vertically, tracked in Tracker: sub-materiality visual deviations (revisit in bulk) #1874; they are not claimed to be rasterization.
• GT: assets/bugfixes/issue-1884/gt.jpg
• Before: assets/bugfixes/issue-1884/before.jpg
• After: assets/bugfixes/issue-1884/after.jpg
• Native: None

Visual comparison

GT	Before	After

Required inspection

• Rendered all evidence at 150 DPI or higher
• Stored progressive JPEG quality 86 assets with metadata stripped
• Used Codex/Claude vision to inspect the full GT/output pages, diff, and matched crops
• Inspected matched region crops at full resolution
• Ran compare_layout.py --audit --fine-shift PT and dispositioned every fine/large text-instance shift, rectangle geometry deviation, painted-text visibility mismatch, and visible-fill occlusion
• Ran compare_render.py --cluster-report PATH --strict-clusters and dispositioned every material 5% fuzz diff cluster by explicit ID
• Inventoried hairlines and border dash styles
• Inventoried font weight, italic, and underline emphasis

Deviation audit

Check	Result
Page count/order	Matches GT
Element presence	Matches GT — both cells and following paragraph are present in every probe.
Position/size	Remaining: #1874 — text anchors differ by at most 0.22pt horizontally and 0.167pt vertically; the extra 5pt inset is fixed.
Rotation/flip	No deviation observed
Fill	Matches GT
Stroke/border	Matches GT
Shape outline geometry	Matches GT
Text content	Matches GT
Font family/weight/style	Matches GT
Text color	Matches GT
Alignment	Remaining: #1874 — text anchors differ by at most 0.22pt horizontally and 0.167pt vertically; the extra 5pt inset is fixed.
Line/paragraph spacing	Remaining: #1874 — text anchors differ by at most 0.22pt horizontally and 0.167pt vertically; the extra 5pt inset is fixed.
Clipping/overflow	No deviation observed

Checklist

• Commits include a Signed-off-by line
• PR scope contains one root cause
• Remaining converter or harness deviations each reference an open issue