docs(11-03): record the websockets plugin dissolution (D-16) and the RT-01 client note

- PROJECT.md: websockets is not a separate app plugin; Key Decisions row
- REQUIREMENTS.md: RT-01 names a hand-rolled Centrifugo client (D-12)

.planning/REQUIREMENTS.md

@@ -91,7 +91,7 @@ Requirements for v1 (the Płytarium port). Each maps to roadmap phases. "User" b
 
 ### Realtime (RT)
 
-- [ ] **RT-01**: The websockets plugin publishes to the existing Centrifugo server (gocent) and issues connection and subscription JWTs with the same secret and claims, served at GET /api/realtime/token
+- [ ] **RT-01**: The websockets plugin publishes to the existing Centrifugo server (gocent) and issues connection and subscription JWTs with the same secret and claims, served at GET /api/realtime/token. *Note (D-12, D-16): the Centrifugo client is a hand-rolled `net/http` client in the framework package `lighthouse/centrifugo` rather than the originally named gocent library, and the publisher lives in that framework package rather than an app websockets plugin.*
 - [ ] **RT-02**: A channel-namespace authorizer registry lets plugins register authorizers (collection, wishlist); the server re-validates on every subscribe and channel names never expose raw ids
 - [ ] **RT-03**: A broadcastable model interface emits live patches with bulk-write suppression, separate from durable notifications