fix: persist pending captures in session storage and refine permissions

[pproenca]

Summary

• Move pendingCaptureTabs from in-memory Map to session storage to survive service worker restarts
• Make manifest permissions conditional: offscreen only for Chrome, tabs only for E2E builds
• Disable test-activate page in non-E2E builds for security
• Fix offscreen message listener to use sendResponse callback pattern
• Add quota error handling with automatic cleanup retry in storage utils
• Set allFrames: false explicitly on content script

Test plan

• Unit tests pass (193 tests)
• TypeScript compiles without errors
• ESLint passes
• E2E tests pass in CI
• Extension loads and activates correctly in Chrome
• Pending capture flow resumes after service worker restart

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 10.00000% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.51%. Comparing base (b64f2a7) to head (717580d).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
utils/storage.ts	0.00%	9 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##           master       #5      +/-   ##
==========================================
- Coverage   47.75%   47.51%   -0.25%     
==========================================
  Files          35       35              
  Lines        1562     1572      +10     
  Branches      326      329       +3     
==========================================
+ Hits          746      747       +1     
- Misses        703      712       +9     
  Partials      113      113              

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