fix(xlsx): match native theme tint colors

[developer0hye]

Summary

• use the corrected Excel-compatible theme-tint calculation now merged into the patched umya-spreadsheet v2 branch
• add an application-level regression that resolves the fixture's accent-2 tint="0.7999" fill to native Excel's #F8EFF0
• add fresh 150-DPI GT/before/after evidence for the affected page

The dependency fix uses Excel's 240-step integer HLS quantization instead of a floating-point 255-step transform. It is backported in developer0hye/umya-spreadsheet#9 and proposed upstream in MathNya/umya-spreadsheet#360.

Related issue

Related: #1394

Testing

• cargo test -p office2pdf test_positive_theme_tint_matches_native_excel_hls_quantization
• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets -- -D warnings
• cargo test --workspace
• wasm-pack build crates/office2pdf --target web --features wasm
• (cd crates/office2pdf && TMPDIR=/Volumes/T7/office2pdf-wasm-1394.R5NDo2 wasm-pack test --node --features wasm) — 10 passed
• TMPDIR=/Volumes/T7/office2pdf-wasm-1394.R5NDo2 wasm-pack build crates/office2pdf --target web --features wasm-cjk-font
• (cd crates/office2pdf && TMPDIR=/Volumes/T7/office2pdf-wasm-1394.R5NDo2 wasm-pack test --node --features wasm-cjk-font) — 11 passed
• python3 scripts/compare_layout.py <native-Excel-page-1.pdf> <office2pdf-after.pdf> --page 1 --noise-floor 0.5 --audit — 12 matched text blocks, 0 missing/extra/rewrapped, no shift over 5pt
• python3 scripts/compare_render.py <native-Excel-page-1.pdf> <office2pdf-after.pdf> --page 1 --dpi 150 --audit — histogram intersection 0.9980, colour shift 0.0001, no material axis difference
• inspected full pages, 5% pixel diff, and matched body/footer/right-edge crops directly at 150 DPI
• vector-path audit: all 42 pale body-fill paths changed from #F8F0F1 to native Excel's #F8EFF0

Visual impact

• No rendered PDF change
• Rendered PDF change or visual evidence added
• Reason: The page-1 pale body panel now uses the same theme-tint colour as native Excel.

Visual audit

• Issue: XLSX: a positive theme tint resolves one RGB step lighter than Excel #1394
• Fixture: Gift Budget and Tracker1.xlsx (attachment on Gift Budget and Tracker1.xlsx misc issues #982)
• Page(s): page 1 (Start sheet)
• Renderer and DPI: pdftoppm, 150 DPI
• Evidence mode: fix
• New follow-up issues found in this audit: XLSX: segmented same-colour fills leave a one-pixel seam at a path T-junction #1397
• Model vision findings: Full-page, diff, and matched body crops show the pale panel now matching the GT fill while title, text, spacing, and alignment remain stable. The footer crop retains the independently tracked Normal-font mismatch, and the right-edge crop exposes one white pixel at a segmented-fill T-junction tracked in XLSX: segmented same-colour fills leave a one-pixel seam at a path T-junction #1397.
• GT: assets/bugfixes/issue-1394/gt.jpg
• Before: assets/bugfixes/issue-1394/before.jpg
• After: assets/bugfixes/issue-1394/after.jpg

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 and dispositioned every large text-instance shift
• Ran the 5% fuzz pixel-difference sweep
• Inventoried hairlines and border dash styles
• Inventoried font weight, italic, and underline emphasis

Deviation audit

Check	Result
Page count/order	Matches GT for the audited Start sheet page; the workbook output remains in source sheet order.
Element presence	Matches GT; all page-1 content remains present.
Position/size	Remaining: #1210 — the leading footer run still takes the ambient size and shifts its line box.
Rotation/flip	No deviation observed; page 1 contains no independently rotated or flipped content.
Fill	Remaining: #1397 — all 42 tinted body paths are fixed to #F8EFF0, while one header T-junction retains a one-pixel raster seam.
Stroke/border	Matches GT; no intentional hairline or dashed-border mismatch was found on page 1.
Shape outline geometry	Remaining: #1397 — header outer bounds match, but its same-colour regions remain segmented at one T-junction.
Text content	Matches GT; title, body, note, and footer text are unchanged.
Font family/weight/style	Remaining: #1210 — the footer Normal-font size remains unresolved; title/body and the bold Note emphasis match, with no italic or underline runs.
Text color	Remaining: #1210 — the leading footer run still falls back to black instead of the Normal font's theme colour.
Alignment	Matches GT; page-1 title, body rows, note, and footer keep their alignment.
Line/paragraph spacing	Remaining: #1210 — the footer's unresolved Normal-font size still affects its line box.
Clipping/overflow	Matches GT; no new clipping or overflow appears.

Checklist

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