Adds an end-to-end audio-amplitude pipeline so on-stage speakers'
green ring throbs in time with their voice (closer to Spaces /
Clubhouse than the previous binary "is in speakingNow" indicator).
NestPlayer.play() now takes an onLevel callback and computes the
normalized peak of each decoded 16-bit PCM frame. NestViewModel
exposes audioLevels: StateFlow<Map<String, Float>>; raw 50 Hz
updates from the decode loop are coalesced into a 10 Hz publish
tick (LEVEL_TICK_MS) so the StateFlow doesn't spam recompositions
across a busy stage. The map is cleared on speaker close, on the
speaking-timeout sweep, and on teardown.
In MemberCell the speaking ring's width animates between
AVATAR_RING_WIDTH (3 dp) and MAX_RING_WIDTH (7 dp) via
animateDpAsState, smoothing the tick into a continuous halo.
Muted-publisher and idle states are unchanged.
Adds NestPlayerTest coverage for the new callback (level math +
empty-PCM short-circuit).
Claude
04ee2c3106