fix(combat): persist death and retarget on kill

Keep the velocity-only NPC adaptation inside the locomotion family so authoritative Dead motion remains persistent. Route selection clears through a dedicated combat target controller that reacquires the closest eligible creature when retail Auto Target conditions apply.

Co-Authored-By: Codex <codex@openai.com>

docs/research/2026-07-12-death-and-auto-target-pseudocode.md

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+# Persistent death and post-death Auto Target pseudocode
+
+Sources: Sept 2013 EoR named retail client.
+
+- `ClientCombatSystem::AutoTarget` (`0x0056BC80`)
+- `ClientCombatSystem::RecvNotice_SelectionChanged` (`0x0056BD80`)
+- `CPlayerSystem::SelectNext` (`0x0055F9A0`)
+- `MovementManager::unpack_movement` (`0x00524440`)
+- `CPhysicsObj::MoveOrTeleport` (`0x00516330`)
+
+## Animation authority
+
+```text
+on UpdateMotion(interpretedState):
+    pass the state through MovementManager and CMotionInterp
+    Dead is a persistent substate selected by the motion table
+
+on UpdatePosition(position, velocity):
+    update the physics pose and velocity
+    do not select Ready, Walk, Run, or any other animation
+```
+
+acdream retains a documented AP-80 adaptation for ACE actors that move only
+through position snapshots: velocity may choose a visible locomotion cycle.
+That adaptation is now restricted to replacing only Ready/Walk/Run-family
+states. An authoritative action or substate such as attack, hit reaction, or
+Dead always wins. This preserves the adaptation without allowing a late
+position delta to make a corpse stand again.
+
+## Auto Target after the selected creature dies
+
+```text
+when authoritative Dead motion is applied to the selected object:
+    clear selected object
+    publish SelectionChanged
+
+RecvNotice_SelectionChanged():
+    update target tracking
+    if selected object is zero
+       and combat mode is Melee or Missile
+       and Auto Target is enabled:
+        AutoTarget()
+
+AutoTarget():
+    if a recent valid last-attacked object exists:
+        select it
+    else:
+        SelectNext(forward=true, includeCurrent=true, COMPASS_ITEM)
+
+SelectNext(... COMPASS_ITEM) while in Melee/Missile:
+    reject non-attackable, fellowship, hidden, and out-of-radar candidates
+    rank eligible candidates by the retail weighted spatial distance
+    select the best candidate
+```
+
+The current M2 world-state projection has no retail `lastAttacked` instance-id
+quality, so its existing closest eligible creature scan implements the
+fallback branch. The important lifecycle behavior is exact: authoritative
+death clears selection, and the SelectionChanged consumer reacquires only
+when Auto Target is enabled in Melee/Missile combat.