T12: Collapse duplicated combatant behavior #25

Parent

Restructure spec: #13 (RESTRUCTURE_PLAN.md)

What to build

One shared brother base replacing the player/PlayerNPC copies of respawn and turn-on/turn-off logic; the duplicated enemy idle/pain states and the doubled aim raycast collapse into single-sourced behavior with per-entity parameters only; states stop reaching owner internals by string path. Same behavior, one place to fix.

Acceptance criteria

• Player and PlayerNPC share the brother behavior; the copies are deleted
• Enemy aim logic is single-sourced (one raycast helper, not two)
• Behavior unchanged; covered by tests at the shared seam

Blocked by

• T5 Brothers, combat, and respawn through state and service (T5: Brothers, combat, and respawn through state and service #18)