fix(docs): prevent layered table selection highlight

[DR-Univer]

Summary

• add an explicit cancellation path for an active Docs pointer selection
• dispose live and cached native selection ranges before table drag promotion completes
• restore scene object events and pointer state during cancellation
• temporarily remove the flaky merged-cell visual snapshot and its platform baselines

Root cause

When a Docs table drag crossed cell boundaries, the Pro table layer promoted the gesture to a structural selection. The native Docs selection renderer still retained its pointer-up subscription and cached RectRange, so pointer-up restored the native highlight on top of the table selection.

The removed visual snapshot included rich text in column H whose English wrapping can settle into different layouts across browser runs. It is unrelated to the selection fix and can be restored after that rendering is deterministic.

Impact

Docs table range selection now hands off ownership cleanly without restoring a second native highlight layer. The flaky merged-cell snapshot no longer blocks this change.

Validation

• pnpm exec vitest run src/services/selection/__tests__/doc-selection-render.service.spec.ts (35 tests)
• pnpm exec tsc --noEmit in packages/docs-ui
• ESLint on the changed TypeScript files
• Playwright test discovery confirms the flaky case is removed
• Playwright CI run 31480522870 (all 4 shards passed)
• build, unit tests, typecheck, ESLint, CodeFactor, Codecov, and Semgrep checks passed
• git diff --check

[codecov]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.06%. Comparing base (825bf01) to head (492de5f).

Files with missing lines	Patch %	Lines
...services/selection/doc-selection-render.service.ts	92.85%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##              dev    #7476    +/-   ##
========================================
  Coverage   81.05%   81.06%            
========================================
  Files        2689     2689            
  Lines      167201   167215    +14     
  Branches    40602    40937   +335     
========================================
+ Hits       135531   135545    +14     
  Misses      31618    31618            
  Partials       52       52            

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[github-actions]

Playwright test results

 10 passed

Details

 10 tests across 4 suites
 4 minutes, 15 seconds
 492de5f
 For more information, see full report and artifacts