feat(animation): decompose AnimationController into FSM-based architecture

Replace the 2,200-line monolithic AnimationController (goto-driven,
single class, untestable) with a composed FSM architecture per
refactor.md.

New subsystem (src/rendering/animation/ — 16 headers, 10 sources):
- CharacterAnimator: FSM composer implementing ICharacterAnimator
- LocomotionFSM: idle/walk/run/sprint/jump/swim/strafe
- CombatFSM: melee/ranged/spell cast/stun/hit reaction/charge
- ActivityFSM: emote/loot/sit-down/sitting/sit-up
- MountFSM: idle/run/flight/taxi/fidget/rear-up (per-instance RNG)
- AnimCapabilitySet + AnimCapabilityProbe: probe once at model load,
  eliminate per-frame hasAnimation() linear search
- AnimationManager: registry of CharacterAnimator by GUID
- EmoteRegistry: DBC-backed emote command → animId singleton
- FootstepDriver, SfxStateDriver: extracted from AnimationController

animation_ids.hpp/.cpp moved to animation/ subdirectory (452 named
constants); all include paths updated.

AnimationController retained as thin adapter (~400 LOC): collects
FrameInput, delegates to CharacterAnimator, applies AnimOutput.

Priority order: Mount > Stun > HitReaction > Spell > Charge >
Melee/Ranged > CombatIdle > Emote > Loot > Sit > Locomotion.
STAY_IN_STATE policy when all FSMs return valid=false.

Bugs fixed:
- Remove static mt19937 in mount fidget (shared state across all
  mounted units) — replaced with per-instance seeded RNG
- Remove goto from mounted animation branch (skipped init)
- Remove per-frame hasAnimation() calls (now one probe at load)
- Fix VK_INDEX_TYPE_UINT16 → UINT32 in shadow pass

Tests (4 new suites, all ASAN+UBSan clean):
- test_locomotion_fsm: 167 assertions
- test_combat_fsm: 125 cases
- test_activity_fsm: 112 cases
- test_anim_capability: 56 cases

docs/ANIMATION_SYSTEM.md added (architecture reference).

include/game/game_handler.hpp

@@ -940,7 +940,9 @@ public:
 
     // Spell cast animation callbacks — true=start cast/channel, false=finish/cancel
     // guid: caster (may be player or another unit), isChannel: channel vs regular cast
-    using SpellCastAnimCallback = std::function<void(uint64_t guid, bool start, bool isChannel)>;
+    // castType: DIRECTED (unit target), OMNI (self/no target), AREA (ground AoE)
+    using SpellCastAnimCallback = std::function<void(uint64_t guid, bool start, bool isChannel,
+                                                      SpellCastType castType)>;
     void setSpellCastAnimCallback(SpellCastAnimCallback cb) { spellCastAnimCallback_ = std::move(cb); }
 
     // Fired when the player's own spell cast fails (spellId of the failed spell).

include/game/handler_types.hpp

@@ -40,13 +40,25 @@ struct TalentTabEntry {
 
 // ---- Spell / cast state ----
 
+// Spell targeting classification for animation selection.
+// Derived from the spell packet's targetGuid field — NOT the player's UI target.
+//   DIRECTED — spell targets a specific unit (Frostbolt, Heal, Shadow Bolt)
+//   OMNI     — self-cast / no explicit target (Arcane Explosion, buffs)
+//   AREA     — ground-targeted AoE (Blizzard, Rain of Fire, Flamestrike)
+enum class SpellCastType : uint8_t {
+    DIRECTED = 0,  // Has a specific unit target
+    OMNI     = 1,  // Self / no target
+    AREA     = 2,  // Ground-targeted AoE
+};
+
 struct UnitCastState {
-    bool     casting         = false;
-    bool     isChannel       = false;
-    uint32_t spellId         = 0;
-    float    timeRemaining   = 0.0f;
-    float    timeTotal       = 0.0f;
-    bool     interruptible   = true;
+    bool          casting         = false;
+    bool          isChannel       = false;
+    uint32_t      spellId         = 0;
+    float         timeRemaining   = 0.0f;
+    float         timeTotal       = 0.0f;
+    bool          interruptible   = true;
+    SpellCastType castType        = SpellCastType::OMNI;
 };
 
 // ---- Equipment sets (WotLK) ----