fix(docs): keep cursor stable at document bounds

[DR-Univer]

Summary

• Keep doc cursor movement stable at document boundaries, including Ctrl/Cmd navigation paths.
• Preserve paragraph menu/context menu registration needed by the cursor behavior.
• Add focused coverage for cursor shortcuts, cursor movement, paragraph menu range handling, selection rect conversion, and context menu wiring.

Test Plan

• pnpm --filter @univerjs/docs-ui exec vitest run src/controllers/__tests__/doc-move-cursor.controller.spec.ts src/services/__tests__/doc-paragraph-menu.service.spec.ts src/services/selection/__tests__/selection-utils.spec.ts src/shortcuts/__tests__/cursor.shortcut.spec.ts src/menu/__tests__/context-menu.spec.ts - 5 files, 85 tests passed
• Note: full pnpm --filter @univerjs/docs-ui test was also attempted and failed in unrelated existing view/dependency-loading tests, including missing @univerjs/icons/React module reads and React view assertions outside the changed files.

[github-actions]

View Deployment

#28135277260

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[github-actions]

Playwright test results

 8 passed

Details

 8 tests across 3 suites
 3 minutes, 27 seconds
 7847ffa
 For more information, see full report and artifacts

[codecov]

Codecov Report

❌ Patch coverage is 73.68421% with 80 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.35%. Comparing base (cdae784) to head (7847ffa).

Files with missing lines	Patch %	Lines
...s-ui/src/controllers/doc-move-cursor.controller.ts	71.32%	80 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #7149      +/-   ##
==========================================
+ Coverage   80.28%   80.35%   +0.07%     
==========================================
  Files        2530     2530              
  Lines      152511   152757     +246     
  Branches    35320    35398      +78     
==========================================
+ Hits       122444   122753     +309     
+ Misses      30067    30004      -63     

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