docs: cross-reference sounds.md from voice.md + CLAUDE.md subsystem table

CLAUDE.md

@@ -149,6 +149,7 @@ Before modifying any subsystem, read its spec from `docs/systems/`. After making
 | [dm-system.md](docs/systems/dm-system.md) | DM lifecycle (1-on-1 + group), soft-close/reopen, ownership transfer, federation relay, deterministic federatedId, system messages | DM features, group DM management, DM federation |
 | [spaces.md](docs/systems/spaces.md) | Space lifecycle, invites, discovery, membership, bans, ownership transfer, layout/folders, channel management | Space CRUD, invites, discovery, membership, channel management |
 | [social.md](docs/systems/social.md) | Friend requests, friendships, mutuals, user discovery, friend relay, socialStore cross-instance loading | Friends, social graph, user discovery, mutual calculations |
+| [sounds.md](docs/systems/sounds.md) | System-sound inventory: every file in `packages/web/public/sounds/` mapped to its event + audience, viewer-detection data-channel protocol, message-sound filter, settings hooks | Any sound-effect change, viewer-tracking work, message-sound semantics |
 | [admin.md](docs/systems/admin.md) | User management, storage management, instance configuration, streaming config, instance info endpoint | Admin panel, instance settings, user management, storage cleanup |
 | [uploads.md](docs/systems/uploads.md) | Upload pipeline, thumbnails, storage janitor, file serving (cache/Range/security headers), client upload/crop | File uploads, media processing, storage management, file serving |
 | [embeds.md](docs/systems/embeds.md) | URL extraction, embed classification, provider handling, OG scraping, SSRF protection, image probing, client renderers | Embed/link preview features, metadata fetching, SSRF policy |