fix(pptx): apply paragraph-end font to the final physical line

[developer0hye]

Summary

Seat automatically wrapped PowerPoint paragraphs using the paragraph-end font
only on the final physical line. The startup fixture's first text line and
bullet move from 142pt to 143pt (native: 143.04pt), while its final line keeps
the mark's font seat. Typst retains responsibility for shaping, wrapping and
layout height; completed-frame adjustments keep links and underlines with
their text. Centered and bottom-anchored stories use their local origin.

Native one-factor width and mark-font probes isolate the cause: changing only
the width makes the first baseline 143.04pt when wrapped or 142.08pt when
unwrapped; changing only the end-mark face moves the final wrapped line.
Explicit hard breaks retain their existing line-stack path. Scripted runs
retain their existing behavior until logical lines can be distinguished from
superscript/subscript baselines.

Related issue

Related: #1177. Remaining independent defects: #1581, #1582, #1583, #1584.

Testing

• cargo test --locked --workspace --no-fail-fast: passed (3484 tests; 15 ignored).
• cargo clippy --locked --workspace --all-targets -- -D warnings: passed.
• cargo fmt --all -- --check and git diff --check: passed.
• RED/GREEN regressions for final-line mark seating, centered Korean paragraphs,
  all three wrapped list markers, and link/underline positions. An embedded-font
  regression checks the same behavior without depending on installed Office fonts.
• Fresh native PowerPoint exports and all four comparison axes on eleven pages.
  Searchable text matches (1,608 normalized codepoints; identical codepoint census).

Visual impact

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

Visual audit

• Issue: PPTX: a wrapped slide paragraph seats its first baseline 0.96pt above where PowerPoint does #1177
• Fixture: Four public PPTX fixtures in tests/golden_mocks/business/sources/pptx/: 01_startup_pitch_en.pptx, 03_product_launch_en.pptx, 08_marketing_report_en.pptx, 09_lecture_ko.pptx; concatenated in that order. Full mapping and hashes: assets/bugfixes/issue-1177/README.md.
• Page(s): 1-11
• Renderer and DPI: pdftoppm, 150 DPI; native PowerPoint 16.112.3 GT
• Evidence mode: fix
• Layout audit report: assets/bugfixes/issue-1177/layout-audit.json
• Render cluster reports: assets/bugfixes/issue-1177/render-clusters-page-1.json, assets/bugfixes/issue-1177/render-clusters-page-2.json, assets/bugfixes/issue-1177/render-clusters-page-3.json, assets/bugfixes/issue-1177/render-clusters-page-4.json, assets/bugfixes/issue-1177/render-clusters-page-5.json, assets/bugfixes/issue-1177/render-clusters-page-6.json, assets/bugfixes/issue-1177/render-clusters-page-7.json, assets/bugfixes/issue-1177/render-clusters-page-8.json, assets/bugfixes/issue-1177/render-clusters-page-9.json, assets/bugfixes/issue-1177/render-clusters-page-10.json, assets/bugfixes/issue-1177/render-clusters-page-11.json
• Reference exporter differences: None
• Fine-detail threshold: 0.5pt
• 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: PPTX: top-anchored text snaps to page coordinates instead of its text-box origin #1583, PPTX: wrapped continuation baselines retain unsnapped fractional line offsets #1584
• New follow-up issues found in this audit: PPTX: multiplication sign disables advance-grid rounding for the entire Latin run #1581, PPTX: word-level width rounding drops kerning across spaces #1582, PPTX: top-anchored text snaps to page coordinates instead of its text-box origin #1583, PPTX: wrapped continuation baselines retain unsnapped fractional line offsets #1584
• Model vision findings: Full GT/output pages, diffs, matched region bands, all 40 material-cluster crops and the four fine-shift crops were inspected. The startup first bullet now follows its first text line. Covers retain title weight and fills; startup bars/KPI cards, product chevrons/chart, marketing cards/chart and the Korean panel retain their shapes and content. Thin axes, ticks, bar edges and legend outlines remain present. Product page 2's shifted suffix and marketing page 3's accumulated width drift remain in PPTX: word-level width rounding drops kerning across spaces #1582 and PPTX: multiplication sign disables advance-grid rounding for the entire Latin run #1581; product page 3 and lecture page 2 retain the origin-rounding shifts in PPTX: top-anchored text snaps to page coordinates instead of its text-box origin #1583, and startup's continuation shift remains in PPTX: wrapped continuation baselines retain unsnapped fractional line offsets #1584. Three clusters retain matching geometry/content with only a resampled gold legend-key edge or regular Korean glyph-edge rasterization; every other material cluster references an open issue.
• GT: assets/bugfixes/issue-1177/gt.jpg
• Before: assets/bugfixes/issue-1177/before.jpg
• After: assets/bugfixes/issue-1177/after.jpg
• Native: None

Visual comparison

Each image contains the eleven full pages in collection order.

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: all eleven pages in the documented fixture order.
Element presence	Matches GT: text, markers, shapes and pictures remain present.
Position/size	Remaining: #1581, #1582, #1583, #1584; advance-grid, cross-space kerning, story-origin rounding and continuation-line rounding respectively.
Rotation/flip	Matches GT.
Fill	Matches GT: covers, cards, chart fills and Korean panel.
Stroke/border	Matches GT: thin axes, ticks, legend outlines and bar edges remain present.
Shape outline geometry	Matches GT.
Text content	Matches GT: normalized searchable text and codepoint census agree.
Font family/weight/style	Matches GT: same title/body weights and Korean emphasis in full-scale crops.
Text color	Matches GT.
Alignment	Fixed: first wrapped line and bullet use the nonfinal font seat.
Line/paragraph spacing	Remaining: #1583, #1584; fractional origin and continuation-line rounding.
Clipping/overflow	Matches GT on the original eleven-page fix collection.

Checklist

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