feat: emotive animations + anime speed lines — hit flinch, dance emote (B)

- SkinnedPlayerModel: generic play_oneshot() (generalizes the Land lock),
  Hit and Dance in the clip table (Dance loops), restartable clips
- Hit flinch: victims visibly react on every peer's screen via the existing
  damage broadcast — no new RPC
- Dance emote on B: toggles while grounded and idle, breaks on any movement;
  synced to remotes via synced_is_dancing (all three spawner configs)
- Anime radial speed-lines overlay (canvas shader): fades in past ~1.2x walk
  speed, spikes on dash, widescreen-corrected clear center
- New input action 'emote' (B) in project.godot

11/11 FSM tests, spawn smoke 0 failures.

Co-Authored-By: Claude Fable 5 <[email protected]>

assets/shaders/speed_lines.gdshader.uid

@@ -0,0 +1 @@
+uid://l1bq145iht8