fix(xlsx): honor icon-set cfvo thresholds and their types

[developer0hye]

Summary

Icon-set conditional formatting assigned most cells the wrong band — values landed one band too low. On 10_kpi_tracker_en.xlsx the 3Arrows rule uses type="num" thresholds [0, 0.9, 1.0], but 107% rendered with the middle (yellow) icon and 93% with the low (red) icon instead of green-up / yellow-side (issue #406).

Two root causes:

1. umya-spreadsheet drops the cfvo children. The <cfvo> elements are written as start/end tag pairs (openpyxl style); umya's IconSet reader only matches Event::Empty, so get_cfvo_collection() came back empty and office2pdf fell back to equal-thirds thresholds (the same reader gap fixed for DataBar in fix: read dataBar cfvo and color children written as start/end tags MathNya/umya-spreadsheet#347).
2. office2pdf ignored the cfvo type. Every threshold was computed as min + range·(val/100), treating the value as a percentage even for type="num".

The iconSet cfvo (type, val) pairs are now parsed from the raw worksheet XML (where office2pdf already reads the icon-set type) and each threshold is resolved per its type: num literal, percent a fraction of the range, percentile interpolated over the values, min/max the extremes. umya's typeless cfvos remain a legacy fallback, and equal-thirds the last resort.

Verified on the KPI fixture: every cell's band now matches Excel (107% green-up, 93% yellow-side, 113% green-up, 84% red-down, 103%/130% green-up).

Related issue

Fixes #406

Testing

• cargo test --workspace — green
• Local bulk regression gate — PASS
• New raw-hint tests worksheet_hints_collect_icon_set_cfvo_thresholds, worksheet_hints_do_not_confuse_databar_cfvo_with_icon_set
• New integration test test_cond_fmt_icon_set_num_thresholds_from_start_end_cfvos (rewrites cfvos into start/end tags, asserts the per-band colors)
• Converted 10_kpi_tracker_en.xlsx: bands match Excel

Visual impact

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

Visual audit

• Issue: XLSX: icon set assigns wrong bands (cfvo thresholds dropped and type ignored) #406
• Fixture: 10_kpi_tracker_en.xlsx (synthetic real-world audit set, external)
• Page(s): 1
• Renderer and DPI: pdftoppm, 150 DPI
• Evidence mode: fix
• New follow-up issues found in this audit: None
• GT: assets/bugfixes/issue-406/gt.jpg
• Before: assets/bugfixes/issue-406/before.jpg
• After: assets/bugfixes/issue-406/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
• 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

Deviation audit

Check	Result
Page count/order	Matches GT
Element presence	Matches GT
Position/size	Matches GT
Rotation/flip	No deviation observed
Fill	Matches GT
Stroke/border	Matches GT
Text content	Matches GT
Font family/weight/style	Matches GT
Text color	Fixed (icon band color now matches Excel for every cell)
Alignment	Matches GT
Line/paragraph spacing	Matches GT
Clipping/overflow	Matches GT
Icon glyph weight	Remaining: #377 (thin arrows vs Excel's solid icons)

Checklist

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

🤖 Generated with Claude Code