Add Pathfinder 2e game system mode

Implements PF2e as an alternative game system alongside D&D 5e/5.5e.
Settings modal "Game System" selector switches conditions, bestiary,
stat block layout, and initiative calculation between systems.

- Valued conditions with increment/decrement UX (Clumsy 2, Frightened 3)
- 2,502 PF2e creatures from bundled search index (77 sources)
- PF2e stat block: level, traits, Perception, Fort/Ref/Will, ability mods
- Perception-based initiative rolling
- System-scoped source cache (D&D and PF2e sources don't collide)
- Backwards-compatible condition rehydration (ConditionId[] → ConditionEntry[])
- Difficulty indicator hidden in PF2e mode (excluded from MVP)

Closes dostulata/initiative#19

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/application/src/set-condition-value-use-case.ts

@@ -0,0 +1,20 @@
+import {
+	type CombatantId,
+	type ConditionId,
+	type DomainError,
+	type DomainEvent,
+	setConditionValue,
+} from "@initiative/domain";
+import type { EncounterStore } from "./ports.js";
+import { runEncounterAction } from "./run-encounter-action.js";
+
+export function setConditionValueUseCase(
+	store: EncounterStore,
+	combatantId: CombatantId,
+	conditionId: ConditionId,
+	value: number,
+): DomainEvent[] | DomainError {
+	return runEncounterAction(store, (encounter) =>
+		setConditionValue(encounter, combatantId, conditionId, value),
+	);
+}