[chrisae9]

Summary

Promote 6.4.17 from dev to main. Interrupted guest startups no longer count as loaded playback, and ordinary host updates can trigger one bounded media retry. Include two playback-harness regressions and cancellation/retry diagnostics.

Verification

• Fix and version PRs fix(sync): recover interrupted guest startup #134 and chore(release): prepare 6.4.17 #135 passed required CI, including Node 22/24 quality, CodeQL and container builds.
• Local production build, lint, 173 server tests, 649 frontend tests and expanded sync fuzz passed.
• The previous 6.4.16 behavior was reproduced on the live site with one controlled guest-only cancellation after the real Plex decision: zero frames and a persistent buffering mask.
• Patched frontend verification uses the live room service and own Plex server. Production deployment is held while any movie/episode session is active.