Animate player display inactive transitions and death state

Player display now tracks displayParticipants separately from raw encounter
participants so active->inactive can animate out before removal, and inactive->
active can animate in. This preserves 1-list order, keeps DM display behavior
unchanged, and avoids fading dying/stable participants.

PlayerParticipantCard handles transitions:
- active->inactive: scale/slide/fade out, then parent removes from display list
- inactive->active: scale/slide/fade in
- alive->dead: keep visible with dim/desaturate/red-rim death cue + skull pulse
- dying/stable: full visible, no fade/removal

DisplayView inactive characterization updated to wait for exit animation before
asserting removal. TODO item removed.

TODO.md

@@ -11,18 +11,6 @@ not sure good way to do this
 
 
 
-### FEAT: player display fade transitions for inactive state
-- Inactive is DM-triggered via Mark Inactive.
-- Player display should fade inactive participant out, then remove from display list.
-- Reactivating should fade participant in.
-- DM display keeps inactive participant visible.
-- Dead state does not imply inactive/disabled.
-- Dying/stable must not fade out or leave layout holes.
-- Dead can keep skull/Dead label; create some good visual cues, no removal - but a cool transition to death would be nice.
-
-
-
-
 
 ### TEST GAP: current branch changes need focused coverage
 - Storage `where()` contract: firebase + server adapters should honor `[where('encounterPath','==',x), orderBy('ts','desc'), limit(n)]`.