feat: Implement Invocation System for Invoker attunement

Implements the full Invocation System as per spec §13 with all 22 acceptance criteria:
- Invocation charge meter with passive fill and active drain
- Auto-activation when charge reaches 100 with living enemies
- Guardian selection by elemental bonus × tierMultiplier scoring
- Spell selection from guardian's full element spellbook (not limited to learned)
- Step-down to affordable spells, auto-end when none affordable
- Charge drain during invocation with spell cost and discipline scaling
- Pact affinity cast speed bonus (diminishing returns, max 50%)
- guardian-invocation discipline with 4 perks (efficiency/speed/sustain/mastery)
- Cost multiplier (base 0.1, min 0.05) and drain multiplier (base 1.0, min 0.7)
- Signal recharged on spire exit and reset on descent
- Invocation Panel UI in SpireCombatPage with charge meter and status
- Compact invocation status indicator in SpireCombatControls

Files changed:
- data/disciplines/invoker.ts: Added guardian-invocation discipline definition
- effects/discipline-effects.ts: Added invocationChargeRateBonus, drainRateMultiplier, invocationCostReduction stat keys
- utils/invocation-utils.ts: NEW - All invocation utility functions (guardian selection, spell selection, charge rate, cost/drain multipliers)
- stores/combat-state.types.ts: Added invocationCharge and activeInvocation fields
- stores/combatStore.ts: Added invocation state defaults, resetInvocationState action, partialize, spire exit reset
- stores/combat-invocation.ts: NEW - Extracted invocation tick processing (charge fill/drain, casting, auto-activate/end)
- stores/combat-melee.ts: NEW - Extracted melee combat processing (keeps combat-actions.ts under 400 lines)
- stores/combat-actions.ts: Integrated invocation and melee modules
- __tests__/invocation-system.test.ts: NEW - 39 comprehensive tests
- SpireCombatPage.tsx: Added InvocationPanel between SpireHeader and RoomDisplay
- SpireCombatControls.tsx: Added compact invocation status indicator

All 1235 tests pass (including 39 new invocation tests).

docs/circular-deps.txt

@@ -1,5 +1,5 @@
 # Circular Dependencies
-Generated: 2026-06-12T17:03:20.112Z
+Generated: 2026-06-13T11:02:39.214Z
 Found: 4 circular chain(s) — these MUST be fixed before modifying involved files.
 
 1. 1) data/guardian-encounters.ts > data/guardian-procedural.ts

docs/dependency-graph.json

@@ -1,6 +1,6 @@
 {
   "_meta": {
-    "generated": "2026-06-12T17:03:17.869Z",
+    "generated": "2026-06-13T11:02:37.078Z",
     "description": "Import dependency graph for src/lib/game. Keys are files, values are arrays of files they import.",
     "usage": "To find what a file affects, search for its path in the VALUES. To find what a file depends on, look at its KEY entry."
   },

docs/project-structure.txt

@@ -236,6 +236,7 @@ Mana-Loop/
 │   │   │   │   ├── guardian-names-unique.test.ts
 │   │   │   │   ├── guardian-names.test.ts
 │   │   │   │   ├── hasty-enchanter.test.ts
+│   │   │   │   ├── invocation-system.test.ts
 │   │   │   │   ├── mana-conversion-component-deduction.test.ts
 │   │   │   │   ├── mana-utils.test.ts
 │   │   │   │   ├── melee-auto-attack.test.ts
@@ -386,6 +387,8 @@ Mana-Loop/
 │   │   │   │   ├── combat-actions.ts
 │   │   │   │   ├── combat-damage.ts
 │   │   │   │   ├── combat-descent-actions.ts
+│   │   │   │   ├── combat-invocation.ts
+│   │   │   │   ├── combat-melee.ts
 │   │   │   │   ├── combat-reset.ts
 │   │   │   │   ├── combat-state.types.ts
 │   │   │   │   ├── combatStore.ts
@@ -437,6 +440,7 @@ Mana-Loop/
 │   │   │   │   ├── formatting.ts
 │   │   │   │   ├── guardian-utils.ts
 │   │   │   │   ├── index.ts
+│   │   │   │   ├── invocation-utils.ts
 │   │   │   │   ├── mana-utils.ts
 │   │   │   │   ├── pact-utils.ts
 │   │   │   │   ├── result.ts