fix: merged cell bg not fully ender

[lumixraku]

close https://github.com/dream-num/univer-pro/issues/2716
close #3661
close #3704

Pull Request Checklist

• Related tickets or issues have been linked in the PR description (or missing issue).
• Naming convention is followed (do please check it especially when you created new plugins, commands and resources).
• Unit tests have been added for the changes (if applicable).
• Breaking changes have been documented (or no breaking changes introduced in this PR).

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Playwright test results

 16 passed

Details

 16 tests across 8 suites
 3 minutes, 59 seconds
 190dba2
 For more information, see full report

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 105 lines in your changes missing coverage. Please review.

Project coverage is 31.25%. Comparing base (e8ffd23) to head (190dba2).
Report is 6 commits behind head on dev.

Files with missing lines	Patch %	Lines
...ne-render/src/components/sheets/extensions/font.ts	0.00%	57 Missing ⚠️
...der/src/components/sheets/extensions/background.ts	0.00%	33 Missing ⚠️
...ine-render/src/components/sheets/sheet-skeleton.ts	0.00%	13 Missing ⚠️
packages/core/src/sheets/span-model.ts	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #3671      +/-   ##
==========================================
+ Coverage   31.13%   31.25%   +0.11%     
==========================================
  Files        2254     2259       +5     
  Lines      116685   117125     +440     
  Branches    25642    25761     +119     
==========================================
+ Hits        36326    36603     +277     
- Misses      80359    80522     +163     

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[oumomomo]

CRTL+A选中所有单元格设置背景色，再合并所有单元格不展示背景色
2024_10_9 20_44_20 video.webm

[univer-bot]

Bot detected the issue body's language is not English, translate it automatically. 👯👭🏻🧑‍🤝‍🧑👫🧑🏿‍🤝‍🧑🏻👩🏾‍🤝‍👨🏿👬🏿

CRTL+A selects all cells to set the background color, then merges all cells without displaying the background color
2024_10_9 20_44_20 video.webm

[VicKun4937]

LGTM