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>

apps/web/src/adapters/ports.ts

@@ -1,8 +1,9 @@
 import type {
+	AnyCreature,
 	BestiaryIndex,
-	Creature,
 	CreatureId,
 	Encounter,
+	Pf2eBestiaryIndex,
 	PlayerCharacter,
 	UndoRedoState,
 } from "@initiative/domain";
@@ -31,15 +32,16 @@ export interface CachedSourceInfo {
 
 export interface BestiaryCachePort {
 	cacheSource(
+		system: string,
 		sourceCode: string,
 		displayName: string,
-		creatures: Creature[],
+		creatures: AnyCreature[],
 	): Promise<void>;
-	isSourceCached(sourceCode: string): Promise<boolean>;
-	getCachedSources(): Promise<CachedSourceInfo[]>;
-	clearSource(sourceCode: string): Promise<void>;
+	isSourceCached(system: string, sourceCode: string): Promise<boolean>;
+	getCachedSources(system?: string): Promise<CachedSourceInfo[]>;
+	clearSource(system: string, sourceCode: string): Promise<void>;
 	clearAll(): Promise<void>;
-	loadAllCachedCreatures(): Promise<Map<CreatureId, Creature>>;
+	loadAllCachedCreatures(): Promise<Map<CreatureId, AnyCreature>>;
 }
 
 export interface BestiaryIndexPort {
@@ -48,3 +50,10 @@ export interface BestiaryIndexPort {
 	getDefaultFetchUrl(sourceCode: string, baseUrl?: string): string;
 	getSourceDisplayName(sourceCode: string): string;
 }
+
+export interface Pf2eBestiaryIndexPort {
+	loadIndex(): Pf2eBestiaryIndex;
+	getAllSourceCodes(): string[];
+	getDefaultFetchUrl(sourceCode: string, baseUrl?: string): string;
+	getSourceDisplayName(sourceCode: string): string;
+}