feat: initial implementation v0.1.0 — single player puppet + WASD + map

Composer module: single-player character as puppet (humanoid 4-bone
rig: torso, head, leg_l, leg_r) at world (320, 240) on a 20x20
v0.1-format tilemap.

- WASD direct movement, normalized for diagonals, 120 px/s.
- Camera-chase via lib-core.camera target-provider (camera follows
  puppet position frame-to-frame).
- Idle and walk keyframe animations: idle is a 2s torso-sway on the
  upper track; walk is a 0.6s leg-cycle on the lower track.
- Animation-state transitions driven by movement input: walk while
  WASD-active, idle when released.
- Headtrack: head bone (marked look_at: true in rig) rotates each
  frame to face the mouse cursor's world position via
  puppet.set_look_target.
- ESC -> launcher.

CI hooks (env-var-gated, no-op in normal play):
- SPOREL_CI=1: emits 'vagrant: frame_avg_ms=N' after 60 frames and
  'vagrant: render_frame_ok' per frame from the render hook, then
  engine.exit(0). Smoke stages consume these markers.

animations/walk.anim.json

@@ -0,0 +1,11 @@
+{
+    "id": "walk",
+    "track": "lower",
+    "duration": 0.6,
+    "loop": true,
+    "keyframes": [
+        { "t": 0.0, "leg_l": { "angle": -15 }, "leg_r": { "angle":  15 } },
+        { "t": 0.3, "leg_l": { "angle":  15 }, "leg_r": { "angle": -15 } },
+        { "t": 0.6, "leg_l": { "angle": -15 }, "leg_r": { "angle":  15 } }
+    ]
+}