#9513 improvement(extension): document browser data handling and limited use

Summary

• Document browser extension capture, attachment transfer, retention, site access, and Chrome Web Store Limited Use in the existing privacy policy.
• Preload the assistant authorization module in its security tests so cold module compilation occurs before the test deadline. Keep all assertions and time limits unchanged.

Type of Change

• Improvement

Testing

• Root test gate: 42,158 tests passed, 8 existing skips across 3,732 files; all 20 workspace tasks passed.
• Focused assistant execution suite: 9 tests passed. The credential-resolution test runs in 17ms after moving compilation outside its deadline.
• Root lint, 29 workspace type-checks, all 62 audits, generated artifacts, and block-registry validation passed.
• Cleanup and test-audit completed. Production browser QA verified page capture, attachment preview/removal, sending, chat history, and continuation in the full app.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing (new tests pass the test-audit authoring gate)
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)