playlists(#37): foundation — kind-30082 schema, builder, pure service + tests

First slice of creator playlists. Adds a bitvid-native addressable playlist
event and the pure, hermetic core that builds/parses/mutates it. No UI or network
yet — those land in follow-up commits.

- nostrEventSchemas.js: PLAYLIST_KIND=30082 (+ NOTE_TYPES.PLAYLIST, BASE_SCHEMAS
  entry) and buildPlaylistEvent(). Data lives in tags: d (id), title/description/
  image, and ordered `a` refs (30078:pubkey:d) to videos; order = tag order;
  repeated refs deduped. Deliberately NOT NIP-51's 30005 "video curation set" —
  bitvid already reads 30005 as legacy interest-sets, so reuse would collide.
- js/playlists/playlistService.js: parsePlaylistEvent, buildPlaylist, and
  immutable add/remove/reorder item helpers + videoCoordinate() (reuses the
  canonical buildVideoAddressPointer, same 30078 contract as the zap fix) +
  generatePlaylistId(). Pure — fully unit-testable with no relays/signer.
- tests/playlist-service.test.mjs: 12 scenarios (build tags + order + dedup,
  d-tag required, parse structure/rejects/defaults, build→parse round-trip,
  add/remove/reorder immutability + clamping, coordinate derivation incl. the
  kind-0 internal-object case).
- docs/nostr-event-schemas.md: catalogue row for the new kind.

Schema validation, lint, and build all pass; tests 12/12.

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

docs/nostr-event-schemas.md

@@ -197,6 +197,7 @@ Video posts should treat `videoRootId` as the stable series identifier that rema
 | Zap request (`NOTE_TYPES.ZAP_REQUEST`) | `9734` | `['p', <recipient pubkey>]` plus optional `['e', <event id>]`, `['a', <coordinate>]`, `['amount', <msats>]`, `['lnurl', <bech32>]`, and `['relays', ...]` for receipt publishing | Optional plaintext zap note |
 | Zap receipt (`NOTE_TYPES.ZAP_RECEIPT`) | `9735` | `['bolt11', <invoice>]`, `['description', <zap request JSON>]`, `['p', <recipient pubkey>]` plus optional `['e', <event id>]` and `['a', <coordinate>]` | Empty content; receipts are published by the recipient's LNURL server |
 | Zap tally (`NOTE_TYPES.ZAP_TALLY`) | `30081` (addressable, `d = payment_hash`) | `['d', <payment_hash>]`, `['p', <recipient>]`, optional `['e', <event id>]`/`['a', <coordinate>]`, `['amount', <msats>]`, `['bolt11', <invoice>]`, `['preimage', <hex>]`, `['description', <zap request JSON>]`, `['client', 'bitvid']`, `['t', 'zap']` | bitvid-native, payer-signed, **preimage-verified** stand-in for a 9735 when the recipient's wallet doesn't publish one. Verified via `sha256(preimage)==payment_hash` + `description_hash==sha256(zapRequest)`. Counted alongside 9735s (deduped by `payment_hash`). See `docs/zap-tally-plan.md`. |
+| Playlist (`NOTE_TYPES.PLAYLIST`) | `PLAYLIST_KIND` (`30082`, addressable, `d = playlist id`) | `['t','playlist']`, `['d', <playlist id>]`, optional `['title', ...]`/`['description', ...]`/`['image', ...]`, then **ordered** `['a', '30078:pubkey:d']` refs per video (`['e', <event id>]` also accepted). Item order = tag order. | Creator-curated video playlist (#37). bitvid-native — deliberately NOT NIP-51's `30005` "video curation set", which bitvid already reads as legacy interest-sets (would collide). Built/parsed by `js/playlists/playlistService.js`. |
 | HTTP Auth (`NOTE_TYPES.HTTP_AUTH`) | `27235` | `['u', <url>]`, `['method', <http method>]`, `['payload', <payload hash>]` | Optional plaintext content (NIP-98 recommends empty, but implementations may vary) |
 | Report (`NOTE_TYPES.REPORT`) | `1984` | `['e', <event id>, <report type>]`, `['p', <pubkey>, <report type>]`, and optional `['t', <report type>]` | Plaintext report reason |