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.
medievalshell