fix(#275): classics timeout and subtitle vtt noise

[DSanich]

Summary

This PR fixes two production-facing feed stability issues:

1. Subtitle VTT fallback requests were generating noisy Sentry errors (422) for optional subtitle assets.
2. The Discovery Classic tab could fail to load when randomized pagination started at high offsets that timeout on the backend.

Problems Addressed

1) Subtitle VTT noise in Sentry

Optional subtitle CDN endpoints (/vtt) can return 404/410/422 when subtitles are not available.
These were being captured as failed HTTP errors and surfaced as production noise.

2) Classic feed startup failures

Classic feed startup uses randomized offset pagination.
High offsets (example: offset=312) are currently unstable and can return backend timeout errors, which caused blank/error first loads for users.

What Changed

Subtitles

• Updated subtitle loading logic in useSubtitles to:
  • avoid blind /vtt probing for videos without text-track metadata;
  • only use CDN VTT fallback when a text track is actually advertised;
  • treat 404/410/422 as benign "no subtitles" outcomes.

Sentry filtering

• Added a narrow Sentry filter to drop only benign subtitle VTT events:
  • URL matches media.divine.video/*/vtt
  • status code is one of 404, 410, 422
• Non-benign failures (e.g. 500) are still reported.

Classics feed stabilization

• Reduced classics randomization window to a lower, stable range to avoid high-offset timeout-prone queries.
• Added test coverage for the classics randomization configuration.

Files

• src/hooks/useSubtitles.ts
• src/hooks/useSubtitles.test.ts
• src/lib/sentry.ts
• src/lib/sentry.test.ts
• src/hooks/useVideoProvider.ts
• src/hooks/useVideoProvider.test.ts

Closes #275

[github-actions]

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Property	Value
Preview URL	https://5e8dd481.divine-web-fm8.pages.dev
Commit	492ef30
Branch	fix/275-classics-timeout-and-subtitle-vtt-noise