Phase 2: ECS foundation — world, components, systems, bridge

- bitECS world with time tracking (delta, elapsed, tick)
- 5 components: Position, Velocity, SpriteRef, Health, ChemicalComposition
- Movement system (velocity * delta) + bounce system (boundary reflection)
- Health system with damage, healing, death detection
- Entity factory (createGameEntity/removeGameEntity)
- Phaser bridge: polling sync creates/destroys/updates circle sprites
- GameScene: 20 colored circles bouncing at 60fps
- BootScene: click-to-start transition, version bump to v0.2.0
- 39 ECS unit tests passing (74 total)

Co-authored-by: Cursor <cursoragent@cursor.com>

src/ecs/components.ts

@@ -0,0 +1,36 @@
+/**
+ * ECS Components — plain objects with number arrays (bitECS 0.4 pattern)
+ *
+ * Components define the data schema for entities.
+ * Systems read/write component data.
+ * Bridge syncs component data to Phaser rendering.
+ */
+
+/** World position in pixels */
+export const Position = {
+  x: [] as number[],
+  y: [] as number[],
+};
+
+/** Movement velocity in pixels per second */
+export const Velocity = {
+  vx: [] as number[],
+  vy: [] as number[],
+};
+
+/** Visual representation — used by bridge to create/update Phaser objects */
+export const SpriteRef = {
+  color: [] as number[],   // hex color (e.g. 0x00ff88)
+  radius: [] as number[],  // circle radius in pixels
+};
+
+/** Entity health — damage, healing, death */
+export const Health = {
+  current: [] as number[],
+  max: [] as number[],
+};
+
+/** Link to chemistry system — stores atomic number of primary element */
+export const ChemicalComposition = {
+  primaryElement: [] as number[],  // atomic number (e.g. 11 for Na)
+};