Add hashtag preference schema and feature flag

docs/nostr-event-schemas.md

@@ -147,6 +147,7 @@ import { updateWatchHistoryListWithDefaultClient } from "./nostrWatchHistoryFaca
 | Watch history chunk (`NOTE_TYPES.WATCH_HISTORY_CHUNK`) | `WATCH_HISTORY_KIND` (default `30079`, clients also read legacy `30078`) | `['d', <snapshotId:index>]`, `['encrypted','nip04']`, `['snapshot', <id>]`, `['chunk', <index>, <total>]`, optional leading `['head','1']` on the first chunk, pointer tags for each item, plus schema append tags | NIP-04 encrypted JSON chunk (`{ version, snapshot, chunkIndex, totalChunks, items[] }`) |
 | Subscription list (`NOTE_TYPES.SUBSCRIPTION_LIST`) | `30002` | `['d', 'subscriptions']` | NIP-04 encrypted JSON `{ subPubkeys: string[] }` |
 | User block list (`NOTE_TYPES.USER_BLOCK_LIST`) | `30002` | `['d', 'user-blocks']` | NIP-04 encrypted JSON `{ blockedPubkeys: string[] }` |
+| Hashtag preferences (`NOTE_TYPES.HASHTAG_PREFERENCES`) | `30005` | `['d', 'bitvid:tag-preferences']` plus schema-appended `['encrypted','nip44_v2']` | NIP-44 encrypted JSON `{ version, interests: string[], disinterests: string[] }` |
 | Admin moderation list (`NOTE_TYPES.ADMIN_MODERATION_LIST`) | `30000` | `['d', 'bitvid:admin:editors']`, repeated `['p', <pubkey>]` entries | Empty content |
 | Admin blacklist (`NOTE_TYPES.ADMIN_BLACKLIST`) | `30000` | `['d', 'bitvid:admin:blacklist']`, repeated `['p', <pubkey>]` entries | Empty content |
 | Admin whitelist (`NOTE_TYPES.ADMIN_WHITELIST`) | `30000` | `['d', 'bitvid:admin:whitelist']`, repeated `['p', <pubkey>]` entries | Empty content |
@@ -157,6 +158,17 @@ If you introduce a new Nostr feature, add its schema to
 `js/nostrEventSchemas.js` so that the catalogue stays complete and so existing
 builders inherit the same debugging knobs.
 
+### Hashtag preference lists
+
+Hashtag preference events (`NOTE_TYPES.HASHTAG_PREFERENCES`) live on a
+replaceable `30005` list with a stable identifier tag of
+`['d','bitvid:tag-preferences']`. The builder appends `['encrypted','nip44_v2']`
+so downstream clients can detect that the payload is encrypted. The `content`
+field must be a NIP-44 ciphertext representing the JSON shape
+`{ version, interests: string[], disinterests: string[] }`, allowing clients to
+share their preferred and muted hashtags without exposing the raw preferences on
+relays.
+
 ### NIP-71 rollout
 
 bitvid now emits a paired NIP-71 event (kind `21` for long-form, `22` for short