feat: add Microsoft Excel style theme palette

[Copilot]

• Analyze existing theme structure in /packages/s2-core/src/theme
• Understand palette structure (basicColors, semanticColors, others)
• Review existing palettes (default, gray, colorful, dark)
• Understand how PALETTE_MAP registers themes
• Create Microsoft Excel theme palette file (excel.ts)
• Register Excel palette in PALETTE_MAP
• Add G2 theme type mapping for Excel theme
• Add test coverage for the new Excel theme
• Manually verify the theme renders correctly
• Run code review (passed)
• Run CodeQL security scan (no alerts)
• Add Excel theme example to s2-site demos
• Fix hover/selection colors to match Excel style

Summary

This PR adds a new theme palette that replicates the default visual style of Microsoft Excel spreadsheets.

Changes

• Created new excel.ts palette file in /packages/s2-core/src/theme/palette/
• Registered the Excel palette in PALETTE_MAP
• Added G2 theme type mapping for Excel theme
• Updated theme tests to include the new Excel theme
• Added Excel theme example in s2-site/examples/theme/default/demo/

Excel Theme Colors (Updated)

Color	Usage
#217346	Brand Color (Excel green)
#E6E6E6	Header Background
#D4D4D4	Gridline Color
#FFFFFF	Cell Background
#F2F2F2	Hover/Selected Background (gray)
#D9D9D9	Header Hover Background (gray)
#217346	Selection Border (Excel green)
#0563C1	Link Color (Excel hyperlink blue)
#000000	Text Color

Usage

import { PivotSheet, ThemeCfg } from '@antv/s2';

const themeCfg: ThemeCfg = {
  name: 'excel'
};

const s2 = new PivotSheet(container, dataCfg, { themeCfg });

Preview

Original prompt

Act as a frontend developer. Your task is to create a new theme object for the AntV S2 spreadsheet library. This theme must perfectly replicate the default visual style of Microsoft Excel. Use the existing S2 theme structure as your starting point. Pay close attention to gridline colors, header styles (background, font), and the cell selection styles. Read [packages/s2-core/src/theme] and start

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[Alexzjt]

@copilot 在s2-site/examples/theme/default/demo处增加对应的示例。

[Copilot]

@copilot 在s2-site/examples/theme/default/demo处增加对应的示例。

Added the Excel theme example at s2-site/examples/theme/default/demo/excel.ts and updated meta.json with the new demo entry (commit c7fa136).

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.61%. Comparing base (ecdc9c8) to head (34ace9d).
⚠️ Report is 736 commits behind head on next.

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #3268      +/-   ##
==========================================
- Coverage   75.77%   75.61%   -0.16%     
==========================================
  Files         257       51     -206     
  Lines       11994     1505   -10489     
  Branches     2464      285    -2179     
==========================================
- Hits         9088     1138    -7950     
+ Misses       1398      216    -1182     
+ Partials     1508      151    -1357     

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[Alexzjt]

@copilot 配色还是有问题，hover到单元格之后，被hover的单元格border应该是绿色系，background颜色应该接近灰色。选中之后的background颜色也不对。参考Excel的配色重新调整颜色

[github-actions]

Size Change: +114 B (+0.02%)

Total Size: 628 kB

Filename	Size	Change
./packages/s2-core/dist/s2.min.js	263 kB	+114 B (+0.04%)

ℹ️ View Unchanged

Filename	Size
./packages/s2-core/dist/s2-extends.min.js	158 kB
./packages/s2-core/dist/s2.min.css	581 B
./packages/s2-react-components/dist/s2-react-components.min.css	2.55 kB
./packages/s2-react-components/dist/s2-react-components.min.js	124 kB
./packages/s2-react/dist/s2-react.min.css	1.3 kB
./packages/s2-react/dist/s2-react.min.js	38.5 kB
./packages/s2-vue/dist/s2-vue.min.css	1.59 kB
./packages/s2-vue/dist/s2-vue.min.js	38.3 kB

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[Copilot]

@copilot 配色还是有问题，hover到单元格之后，被hover的单元格border应该是绿色系，background颜色应该接近灰色。选中之后的background颜色也不对。参考Excel的...

Updated the Excel theme colors (commit 8ef2f8f):

• Hover/Selected background: Changed from #D6EAF8 (light blue) to #F2F2F2 (Excel light gray)
• Header hover: Changed from #C4D7B2 (light green) to #D9D9D9 (gray)
• Selection border: Changed from #000000 (black) to #217346 (Excel green)

[github-actions]

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