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/components/source-fetch-prompt.tsx

@@ -2,6 +2,7 @@ import { Download, Loader2, Upload } from "lucide-react";
 import { useId, useRef, useState } from "react";
 import { useAdapters } from "../contexts/adapter-context.js";
 import { useBestiaryContext } from "../contexts/bestiary-context.js";
+import { useRulesEditionContext } from "../contexts/rules-edition-context.js";
 import { Button } from "./ui/button.js";
 import { Input } from "./ui/input.js";
 
@@ -14,11 +15,13 @@ export function SourceFetchPrompt({
 	sourceCode,
 	onSourceLoaded,
 }: Readonly<SourceFetchPromptProps>) {
-	const { bestiaryIndex } = useAdapters();
+	const { bestiaryIndex, pf2eBestiaryIndex } = useAdapters();
 	const { fetchAndCacheSource, uploadAndCacheSource } = useBestiaryContext();
-	const sourceDisplayName = bestiaryIndex.getSourceDisplayName(sourceCode);
+	const { edition } = useRulesEditionContext();
+	const indexPort = edition === "pf2e" ? pf2eBestiaryIndex : bestiaryIndex;
+	const sourceDisplayName = indexPort.getSourceDisplayName(sourceCode);
 	const [url, setUrl] = useState(() =>
-		bestiaryIndex.getDefaultFetchUrl(sourceCode),
+		indexPort.getDefaultFetchUrl(sourceCode),
 	);
 	const [status, setStatus] = useState<"idle" | "fetching" | "error">("idle");
 	const [error, setError] = useState<string>("");