fix(mentor): show share button to anonymous users

[conradmugabe]

Anonymous users (who open a chat via a shareable token link rather than logging in) were unable to share a chat because the share button was gated behind isLoggedIn(). The backend now authorizes anonymous principals on the session-sharing endpoint, so gate the button only by the read-only shared-chat view.

Checklist

• Tests were added/updated according to the feature/bugfix/change made
• Version was rolled according to semver requirements
• API endpoints openapi schema was updated if applicable

Changes

• Closes https://github.com/iblai/iblai-platform/issues/1546

[mamigot]

Claude finished @conradmugabe's task —— View job

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E2E Coverage Review ✅

Tasks:

• Dismiss stale REQUEST_CHANGES reviews from bot
• Identify what changed in this PR
• Run mechanical coverage check
• Read current coverage state
• Apply decision logic and post GitHub review

PR Details:

• Branch: fix/1546 -> main
• Files changed: 3 files (CHANGELOG.md, test file, component file)
• Change: Fix share button visibility for anonymous users

Analysis:

• No new page.tsx files detected
• Changes are to existing components only:
  • components/chat/ai-message-bubble.tsx - component logic change
  • components/chat/__tests__/ai-message-bubble.test.tsx - test updates
  • CHANGELOG.md - changelog entry

Coverage Check Results:

• ✅ Mechanical coverage check PASSED
• ✅ No coverage regression (403 checkpoints maintained)
• ✅ All existing app routes remain covered (24/24 files mapped, 100%)
• ✅ No new routes requiring coverage

Decision: This falls under CASE E - No new page.tsx files and mechanical check passed.

Result: ✅ PR APPROVED - No E2E coverage issues detected.

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[mamigot]

✅ E2E Coverage — No Issues

No new app routes were introduced. All existing coverage is intact.