fix(feed): filter cached audio-only notes at render + hydration, not just ingest

The convert-time guard (17b48cbf) only blocks FRESH events. Audio notes cached
before it existed are rehydrated straight from IndexedDB/localStorage as
already-converted video objects (`sig: "unavailable (cached)"`), bypassing
convertEventToVideo — so they kept showing in the main feed and channel grids.

Extract the audio check into a reusable object-level predicate
`isAudioOnlyVideoObject(video)` (url + magnet + imeta tags) and apply it at every
boundary a cached object can slip through:
  - convertEventToVideo now delegates to it (fresh ingest, unchanged behavior)
  - PersistenceManager.applyCachedPayload drops audio-only on hydration (purges
    the cache going forward)
  - NostrClient.getActiveVideos filters it (main feed, immediate effect)
  - nostrService.shouldIncludeVideo filters it above the viewer-is-author
    short-circuit (channel/author grids, incl. the creator's own channel)

Audio-only = no magnet AND no imeta `m video/*` AND (imeta `m audio/*` OR an
unambiguous audio url); `.ogg` alone stays video. Bumped client.js size baseline
(+6 lines). Tests: video-schema-and-conversion (+3 predicate scenarios, 11/11);
nostr-service + ingest-adapter suites green. Lint + build clean. TODO #60.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

scripts/check-file-size.mjs

@@ -30,7 +30,7 @@ const GRANDFATHERED = {
   "js/ui/components/VideoModal.js": 4976,
   "js/app.js": 5602,
   "js/channelProfile.js": 5806,
-  "js/nostr/client.js": 4356,
+  "js/nostr/client.js": 4362,
   "js/ui/components/VideoCard.js": 3129,
   "js/nostrEventSchemas.js": 3541,
   "js/ui/loginModalController.js": 2552,