fix: preserve declared chart series stroke geometry

[developer0hye]

Summary

Preserve the chart series' declared cap, join and miter limit through parsing and rendering. Plot lines and legend samples now use the same geometry, matching native Excel's round/flat/square and round/miter/bevel controls. Values, width, color and marker paint are preserved.

Related: #1590. Related chart-style inheritance remains tracked separately in #1593.

Testing

• The compiled-frame regression fails before the fix and passes afterward for 18 line, mixed column/line, and radar cases, checking both plot and legend strokes. Separate parser tests prevent nested marker/data-point/label styles from supplying series geometry.
• cargo test --locked --workspace --no-fail-fast: 3,495 passed, 15 ignored, none failed.
• cargo clippy --locked --workspace --all-targets -- -D warnings, cargo fmt --all --check, and git diff --check: passed.
• Seven required native Excel 16.112.3 cases match after the fix. Re-zip controls and all native integrity checks pass. A final-quit export error is independently tracked in Native Excel exporter reports completed batches as failed when final quit is cancelled #1592; completed exports were preserved and verified.
• Fifteen before/after cases preserve all other paint primitives and both text/layout findings. Page 1 is unchanged. Six-page 300-DPI audit: all 2,533 material clusters have explicit passing dispositions. Default extraction retains baseline table reading-order differences and ten extra space-census entries; pdftotext -layout has matching non-whitespace text.
• Documentation freshness review: PASS. Reproduction: scripts/probes/issue-1590-series-stroke.json and the evidence README.

Visual impact

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

Visual audit

• Issue: Charts: series strokes drop declared round caps and joins #1590
• Fixture: tests/fixtures/xlsx/issue_1181_fit_to_height.xlsx; series-stroke variants in scripts/probes/issue-1590-series-stroke.json
• Page(s): 1-6
• Renderer and DPI: pdftoppm, 300 DPI; native Excel 16.112.3
• Evidence mode: fix
• Layout audit report: assets/bugfixes/issue-1590/layout-audit.json
• Render cluster reports: assets/bugfixes/issue-1590/render-clusters-page-1.json, assets/bugfixes/issue-1590/render-clusters-page-2.json, assets/bugfixes/issue-1590/render-clusters-page-3.json, assets/bugfixes/issue-1590/render-clusters-page-4.json, assets/bugfixes/issue-1590/render-clusters-page-5.json, assets/bugfixes/issue-1590/render-clusters-page-6.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
• New follow-up issues found in this audit: Native Excel exporter reports completed batches as failed when final quit is cancelled #1592, Charts: omitted series stroke properties do not inherit the related chart style #1593
• Model vision findings: Full six-page GT/output/diff contexts and original-scale endpoint, June-join and marker crops show native-matching declared round/flat/square caps and round/miter/bevel joins. The cap/join changes preserve the series vertices, width, color and marker paint. All GT pixels and all output/diff pixels outside the series strip are unchanged; page 1 is wholly unchanged. Prior individually reviewed text/rule/sparkline crops retain their exact pixel and cluster evidence. The marker remains offset (XLSX: worksheet chart markers omit native raster placement #1577) with softer native bitmap edges; worksheet/chart placements remain tracked below. Final 300-DPI JPEG title, table/hairline and endpoint crops remain legible. All 2,533 material clusters are explicitly dispositioned.
• GT: assets/bugfixes/issue-1590/gt.jpg
• Before: assets/bugfixes/issue-1590/before.jpg
• After: assets/bugfixes/issue-1590/after.jpg
• Native: None
• Compare: 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	Remaining: #1592 native exporter reports final-quit cancellation after completed exports. Verified collection matches GT: original two sheets plus four deliberate series-stroke probes. The omitted-limit control matches page 5's complete paint trace.
Element presence	Remaining: #1566 omitted worksheet separators. Series, markers, axes and labels preserve their source-defined presence.
Position/size	Remaining: #1272 chart frame, #1542 drawing origin, #1543 fitted column width, #1545 row text, #1550 title height, #1552 footer, #1577 cached marker value.
Rotation/flip	No deviation observed
Fill	Matches GT: series color and opaque marker paint are preserved.
Stroke/border	Remaining: #1564 worksheet rule thickness/placement, #1566 missing separators, #1593 related-style inheritance when a local property is absent. Fixed: explicit series caps, joins and miter limits now match native; gray axes, teal totals and brown rules retain their paint.
Shape outline geometry	Remaining: #1272 chart frame and #1550 title band. Fixed: declared series cap/join geometry; marker diameter and outline preserved.
Text content	Matches GT: non-whitespace sequence under pdftotext -layout; narrow-cell ##### totals retained. Default extraction retains baseline reading-order differences and ten extra space-census entries.
Font family/weight/style	Matches GT: Arial bold title, Trebuchet instructions/expense labels, Cambria headings/months and Aptos footer retain emphasis.
Text color	Matches GT: white title, teal headings/totals, gray body, orange negatives and brown expense labels.
Alignment	Remaining: #1542 drawing labels, #1545 row seating, #1550 title/content, #1552 footer, #1577 marker origin.
Line/paragraph spacing	Remaining: #1545 row seating and #1551 wrapped note pitch.
Clipping/overflow	No deviation observed beyond matching native narrow-cell ##### totals.

Checklist

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