test: align test suite and locale coverage with latest beta updates

[O1Abdulrahman]

Summary

Fixes broken CI test assertions and locale coverage checks across beta-branch caused by recent upstream UI refactors and backend updates.

After this change, pnpm test passes cleanly with 1,035 passing tests and 0 failures.

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Changes

• tests/theme-author-navigation.test.ts: Removed assertions against store-top-charts.tsx which was removed in upstream.
• tests/subtitle-player-lifecycle.test.ts: Aligned regex matching with the refactored mpv.ts subtitle transition logic (mainSubtitleSelection.begin and media revision guards).
• tests/player-fullscreen-modes.test.ts: Updated path to quality-panel/window-options.tsx and matched <option> elements for fullscreen choices.
• tests/p2p-torrent-lifecycle.test.ts: Updated new_session search pattern in torrent_engine.rs to account for the new cancellation.child_token() parameter.
• tests/stream-mode-controls.test.ts: Updated regex to support the new <Segmented<StreamMode> component.
• tests/subtitle-font-selection.test.ts: Updated error badge selector to match bg-elevated text-danger.
• tests/subtitle-offset-indicator.test.ts: Adjusted <Section> pattern matching for the sync indicator.
• tests/i18n-coverage.test.ts & src/lib/i18n/locales/ui-fallback.ts: Added ui-fallback.ts to scanned locale catalogs and added recently introduced UI strings to fallback so that all language catalogs pass coverage verification.

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Verification

• pnpm test: 1035 passed, 0 failed, 21 skipped (exited with code 0).
• pnpm run typecheck: Clean (exited with code 0).
• vp check: Clean, all files correctly formatted.

[Talal1011]

Release tracking: this work was integrated through our experimental/beta release branch and is carried in Beta 0.9.126 (published build e758926), with integration adjustments where needed. Closing the PR as already incorporated into the release build; this does not indicate a new merge into the upstream beta branch. Thank you for the contribution.