fix(xlsx): resolve worksheet drawing fonts through the workbook theme

[developer0hye]

Summary

• parse a worksheet drawing run's <a:latin typeface=...>, including the +mj-lt and +mn-lt theme placeholders
• fall back to the theme's minor Latin font for runs that name no typeface, as DrawingML specifies
• read the theme's <a:fontScheme> alongside the color palette it already loads
• traverse a sheet page's drawing text boxes when deciding whether to resolve the font search context

Related issue

Fixes #461

Details

Excel writes a shape label's run properties as <a:rPr lang="en-US" sz="1100"/> with no typeface at all. DrawingML resolves an absent <a:latin> to the theme's minor Latin font, but the drawing parser read only sz, b, and i, so every worksheet drawing label rendered in Typst's serif default.

Fixing the parser alone does not change the rendered PDF, because the second half of the same path was also missing. document_requests_font_families inspected a sheet page's header, footer, and table but never its text_boxes. A workbook whose only font request comes from a shape label therefore skipped font-context resolution entirely, and the Typst compile never received the macOS Office font directories that hold Calibri — so the family office2pdf had just asked for silently fell back to the serif default. Both halves are needed for the labels to reach the page in the workbook's font, so both are here.

pdffonts on the regression fixture, before and after:

	before	after
embedded faces	LibertinusSerif-Regular	LibertinusSerif-Regular, Calibri

The remaining Libertinus face is the unstyled A1 title cell, tracked in #462.

Testing

• cargo fmt --all -- --check
• cargo test --workspace
• cargo clippy --workspace --all-targets --all-features
• pdffonts before/after comparison on tests/fixtures/xlsx/theme_color_drawing.xlsx
• pdftoppm -r 150 rendering, matched full-resolution label crops, and magick compare -metric AE -fuzz 5%

Visual impact

• No rendered PDF change
• Rendered PDF change or visual evidence added
• Reason: worksheet drawing labels now render in the workbook theme font.

Visual audit

• Issue: XLSX: worksheet drawing text runs ignore theme font inheritance #461
• Fixture: tests/fixtures/xlsx/theme_color_drawing.xlsx
• Page(s): page 1 of the Excel GT and of the office2pdf output
• Renderer and DPI: pdftoppm, 150 DPI
• Evidence mode: fix
• New follow-up issues found in this audit: XLSX: self-closing <a:rPr/> drops a worksheet drawing run's size, bold, and italic #466
• GT: assets/bugfixes/issue-461/gt.jpg
• Before: assets/bugfixes/issue-461/before.jpg
• After: assets/bugfixes/issue-461/after.jpg

The GT is the native Microsoft Excel export already captured for this fixture in #434, reused unchanged: same workbook, same page, same renderer, same 150 DPI.

Visual comparison

GT	Before	After

Required inspection

• Rendered all evidence at 150 DPI or higher
• Stored progressive JPEG quality 86 assets with metadata stripped
• Inspected matched region crops at full resolution
• Ran the 5% fuzz pixel-difference sweep
• Inventoried hairlines and border dash styles
• Inventoried font weight, italic, and underline emphasis

The 5% fuzz sweep against the size-normalized GT is 290,449 differing pixels before and 290,500 after: the drawing geometry defects tracked in #459 and #460 displace all three shapes and dominate the count, so a font-only change cannot move it. The matched label crops at full resolution show the change directly — the GT and the after image both render accent1 in Calibri, the before image in a serif face. The fixture contains no hairlines, borders, or dashed strokes, and every run is regular weight with no italic or underline.

Deviation audit

Check	Result
Page count/order	Remaining: #459 - Excel emits one page; office2pdf adds a blank second page
Element presence	Matches GT - the title and all three drawing labels are present
Position/size	Remaining: #459 tracks same-row vertical stacking; #460 tracks undersized anchor bounds and cumulative horizontal drift
Rotation/flip	No deviation observed - the fixture contains no rotated or flipped elements
Fill	Matches GT - all three RGB values match Excel exactly after #430
Stroke/border	No deviation observed - the shapes intentionally have no outline or hairline
Text content	Matches GT - all four strings are preserved
Font family/weight/style	Remaining: #462 - the unstyled A1 title keeps the serif default; #466 - a self-closing <a:rPr/> still drops the run size, bold, and italic. The family defect this PR targets is fixed: the three drawing labels now render Calibri, as in Excel
Text color	Matches GT - all text remains black
Alignment	Matches GT - drawing labels remain horizontally and vertically centered
Line/paragraph spacing	No deviation observed - each text region is one regular single-line paragraph
Clipping/overflow	Remaining: #459 - flow-height reservation spills onto a blank second page; no page-1 glyph clipping was found

Checklist

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