E4 — Entities & gameplay systems on ECS

[fredboy]

Goal: all entities + gameplay on ECS; bespoke entity/controller/adapter code deleted.

Scope / deliverables:

• cavedroid:components (Player/Inventory/Food/Armor/Bow/Ai/FluidState/…).
• cavedroid:systems (movement, physics-sync, damage, fluid, fire, grow, spawn, hunger).
• AI on gdx-ai (Behavior Trees + FSM + steering) replacing MobBehavior Passive/Aggressive/Archer/FallingBlock. Drive Timepiece from ClockContext; randomness via seeded source; emit via command bus; AI components ticked in the entityAI phase.
• A* pathfinding over the tile grid — separate, possibly-deferred sub-task (nav graph over loaded chunks, time-sliced).
• cavedroid:actions (UseBucket, UseBed, PlaceSlab, …) using context parameters.
• Delete *WorldAdapter, controllers, *Queue spawn queues.

Definition of Done: mobs/drops/projectiles/player run on ECS; no adapters in the codebase. Per-system tests asserting emitted commands (bulk of coverage).

Depends on: E2, E3

[fredboy]

Reshaped by #157 (ADR 0011): use-block/use-item *Action classes become Lua scripts, not hardcoded Kotlin. Per-tick systems here stay native.