Animate entities from the sheet's states

Idle frames tick on a global clock offset by entity id, walk frames run
on a per-entity clock while the position lerp is in flight, and the sim's
Attacked/Died events drive the attacker's action, the victim's flinch and
a corpse that shows the dead frames for a few seconds. All render-side;
the sim is untouched. The snapshot test can dump a strip of frames.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

notes/roadmap.md

@@ -55,9 +55,15 @@ crate's `tick`/`set_action` interface is the seam a server could be wrapped arou
       See `notes/07-map-loader.md`
 - [x] Tile rendering: chunk-based world rendering straight from `World` (`render_viewport`)
 - [x] Sprite-based entity rendering: entity `type_id` → sprite row in `entities.png`
-      (via the `entities.toml` manifest, see Assets above), idle frame blitted with
-      transparency. Animation (walk while the lerp runs, hit/dead from events) is the
-      next step — the sheet layout and loader already carry the frames.
+      (via the `entities.toml` manifest, see Assets above), blitted with transparency.
+- [x] Sprite animation, purely render-side (`Game::entity_frame`): idle on a global
+      clock offset by entity id (so a flock doesn't blink in unison), walk while the
+      position lerp runs (a per-entity walk clock accumulates across steps so the cycle
+      stays continuous), action 1 on the attacker and hit on the victim for 250 ms from
+      the `Attacked` event, and `Died` leaves a `Corpse` showing the dead frames for a
+      few seconds. Priority: hit > action > walk > idle; missing states fall back to
+      idle. `FRAMES=6 SNAPSHOT=… cargo test -p game dump_frame -- --ignored` dumps a
+      strip of consecutive frames.
 - [x] Hybrid tick loop: 24 Hz base tick, movement in `entity_tick` every 4th tick (6 Hz);
       the game loop drives the sim with a fixed-timestep accumulator. See `notes/06-hybrid-tick-loop.md`
 - [x] Intent model: one scheduled action per entity per movement window (`Sim::set_action`),