feat(communication): add housekeeping find-user-by-name packet pair

TS counterparts to Arcturus' new HK packet pair. Adds
HousekeepingFindUserByNameComposer (OutgoingHeader 9100) and
HousekeepingUserDetailEvent (IncomingHeader 9200) with a parser that
wraps an optional HousekeepingUserDetailData. The data class follows
the flat optional-trailing-field pattern (isMuted / isTradeLocked
read under bytesAvailable guards) so the renderer stays compatible
with a server that hasn't surfaced those manager APIs offline yet.

The parser exposes `found: boolean` and `user: HousekeepingUserDetailData | null`
so a callsite that gets a "user not found" reply can branch without
having to read into an unpopulated data object — the composer writes
`appendBoolean(false)` and stops, the parser sees the false and leaves
`user` null.

Headers 9100..9199 / 9200..9299 reserved for the rest of the HK
packet surface. Composer + event registered in NitroMessages alongside
the existing YouTube-room overrides. `yarn compile:fast` clean, vitest
138/138 green.

packages/communication/src/messages/outgoing/OutgoingHeader.ts

@@ -522,4 +522,7 @@ export class OutgoingHeader
     public static YOUTUBE_ROOM_PLAY = 8001;
     public static YOUTUBE_ROOM_WATCHING = 8002;
     public static YOUTUBE_ROOM_SETTINGS = 8003;
+
+    // Housekeeping (in-client admin panel) — IDs 9100..9199 reserved
+    public static HOUSEKEEPING_FIND_USER_BY_NAME = 9100;
 }