fix(xlsx): preserve category label boundary spaces

[developer0hye]

Summary

Preserve single leading and trailing spaces in standalone category-axis labels. Typst collapsed these literal boundary spaces, so centered month labels ignored part of the source label width. Emit them using the same code-mode string representation already used for consecutive spaces. Apply it to bar, column, line, area, and radar category labels, including rotated labels.

Related: #1567. The existing chart-origin offset and separate label-baseline residual remain tracked in #1542 and #1568.

Testing

• Real-workbook regression fails before the fix and passes afterward: jan retains its single trailing space; year keeps its existing two spaces.
• Five chart-type controls cover leading, trailing, both-boundary, multiple, one-space-only, and absent spaces.
• cargo test --locked -p office2pdf --lib: 2,837 passed.
• cargo test --locked --workspace: 3,469 passed.
• cargo clippy --locked --workspace --all-targets -- -D warnings: passed.
• Identical fixture and lockfile baseline/after with Excel DFonts. Page 1 is pixel-identical at 150 DPI; page 2 changes 16,689 pixels at 300 DPI, confined to the 12 month labels. All 831 canonical drawing primitives preserve geometry and paint. The two-space year label is unchanged.
• January moves from x=187.26976pt to 185.98150pt against native x=186.45680pt. The remaining -0.47530pt difference matches the chart zero-axis origin difference (-0.47501pt); the baseline remains y=347.31837pt against native 347.88pt (Charts: Cambria line-chart category baselines sit 0.56pt above Excel #1568).
• All 55 page-1 and 480 page-2 material clusters have reviewed explicit dispositions; six prior label clusters disappear, with no new cluster. Normalized pdftotext -layout content matches native and baseline on both pages (486 and 2,120 non-whitespace characters).

Baseline: d4d8ef3ff4374126b2b69ce0e8378e0f79adf14f, including the separate axis-font and chart-line alpha fixes. Fixture SHA-256: 2b4a2d8dceda58758593c88409875efbda05780559154c02bd13fef4f7a1c65b; Cargo.lock SHA-256: 750f50c507b281f84b945b09573333ffa02dc45cddd566481af8535ae101e612.

Reproduce conversion with cargo run --locked -p office2pdf-cli -- tests/fixtures/xlsx/issue_1181_fit_to_height.xlsx -o output.pdf --font-path '/Applications/Microsoft Excel.app/Contents/Resources/DFonts'. Compare both pages using scripts/compare_layout.py GT.pdf output.pdf --audit --fine-shift 0.5 --json, and scripts/compare_render.py GT.pdf output.pdf --page P --dpi DPI --fine-shift 0.5 --cluster-report PATH --cluster-dispositions PATH --strict-clusters (150 DPI page 1, 300 DPI page 2).

Visual impact

• Rendered PDF change or visual evidence added

Visual audit

• Issue: Charts: centered category labels lose a single trailing space #1567
• Fixture: tests/fixtures/xlsx/issue_1181_fit_to_height.xlsx (SHA-256 2b4a2d8dceda58758593c88409875efbda05780559154c02bd13fef4f7a1c65b)
• Page(s): 1, 2
• Renderer and DPI: pdftoppm at 150 DPI for page 1 and 300 DPI for page 2; MuPDF trace geometry
• Evidence mode: fix
• Layout audit report: assets/bugfixes/issue-1567/layout-audit.json
• Render cluster reports: assets/bugfixes/issue-1567/render-clusters-page-1.json, assets/bugfixes/issue-1567/render-clusters-page-2.json
• Reference exporter differences: None
• Fine-detail threshold: 0.5pt
• Layout audit page count: Pass
• Layout audit text flow: XLSX: fitted fixed-row cell baselines sit up to 2.16pt above Excel on the budget sheet #1545, XLSX: wrapped Trebuchet MS 10pt lines advance 11.89pt instead of Excel’s 13pt #1551
• Layout audit visible fills: Pass
• Layout audit rectangle geometry: XLSX: an anchored chart's frame sits 12.4pt right of the native export's and 1.9% narrow #1272, XLSX: the Arial 18pt auto title row prints 28pt instead of Excel’s 24pt #1550
• Layout audit large shifts: Pass
• Layout audit fine shifts: XLSX: an anchored chart's frame sits 12.4pt right of the native export's and 1.9% narrow #1272, XLSX charts: fitted drawing foreground keeps the physical page origin #1542, XLSX: fitted fixed-row cell baselines sit up to 2.16pt above Excel on the budget sheet #1545, XLSX: the Arial 18pt auto title row prints 28pt instead of Excel’s 24pt #1550, XLSX: wrapped Trebuchet MS 10pt lines advance 11.89pt instead of Excel’s 13pt #1551, XLSX: a mixed-size Aptos footer remains 0.78pt above its native baseline #1552, Charts: Cambria line-chart category baselines sit 0.56pt above Excel #1568
• New follow-up issues found in this audit: None
• Model vision findings: Inspected both full GT/output pages and diffs, all 65 matched fine-shift crops at full resolution, the final JPEG, and the exact before/after change mask. The 12 single-space month labels now include their source boundary space when centered; January moves left by 1.28826pt. Its remaining -0.47530pt native offset agrees with the existing chart-origin offset in XLSX charts: fitted drawing foreground keeps the physical page origin #1542. The 0.56163pt raised baseline remains Charts: Cambria line-chart category baselines sit 0.56pt above Excel #1568. The year label, font, colors, and all 831 canonical drawing primitives remain unchanged. The only 16,689 changed pixels are in the 12 month labels; page 1 is identical. All six prior material month-label clusters disappear, leaving 535 explicitly dispositioned clusters. Existing worksheet rules, omitted separator lines, marker, frame, fixed-row, and first-page layout defects remain tracked below.
• GT: assets/bugfixes/issue-1567/gt.jpg
• Before: assets/bugfixes/issue-1567/before.jpg
• After: assets/bugfixes/issue-1567/after.jpg
• Native: None
• Compare: None

Visual comparison

Native Excel 16.112.3 exports, verified Excel/Quartz PDF provenance. Page 2 at 300 DPI:

GT	Before	After

The unchanged page-1 native comparison is attached to #1550, #1551, and #1552.

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: two printable sheets retain their native order.
Element presence	Remaining: #1185 marker rendering and #1566 omitted worksheet separator lines. Existing axes and chart grid paths are retained.
Position/size	Remaining: #1272 chart frame, #1542 fitted drawings, #1545 fixed-row text, #1550 title-row height, #1552 footer position, and #1568 category-label baseline. Fixed: source category boundary spaces contribute to label centering.
Rotation/flip	No deviation observed: no transform changes.
Fill	Matches GT: intended series, header, and table fills are unchanged.
Stroke/border	Remaining: #1566 omitted worksheet separator lines; #1564 fitted worksheet rule thickness/placement. Declared chart-line opacity remains 25% and 50%, matching native. Gray table hairlines, teal total rules, and brown category rules retain their paths; no dashed or dotted source rules are lost.
Shape outline geometry	Remaining: #1185 marker, #1272 chart frame, and #1550 title-band height. All 831 canonical primitives retain geometry and paint.
Text content	Matches GT after whitespace normalization of pdftotext -layout; all label/value characters are preserved; the source month categories also retain their significant trailing space.
Font family/weight/style	Matches GT: the existing Cambria major-theme category font is preserved. Bold Cambria section headings, bold Trebuchet expense headings, Arial bold instruction title, and Aptos footer retain their emphasis. No italic or underlined runs are changed.
Text color	Matches GT: chart labels and worksheet text retain their colors.
Alignment	Remaining: #1542 drawing labels, #1545 row text, #1550 first-page content, #1552 footer baselines, and #1568 category-label baseline. Fixed: single boundary spaces are preserved in the aligned label width.
Line/paragraph spacing	Remaining: #1545 fixed-row seating and #1551 wrapped note line pitch.
Clipping/overflow	No deviation observed: no new clipping or overflow; native and output both display ##### in the narrow annual-total cells.