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/settings-modal.tsx

@@ -13,6 +13,7 @@ interface SettingsModalProps {
 const EDITION_OPTIONS: { value: RulesEdition; label: string }[] = [
 	{ value: "5e", label: "5e (2014)" },
 	{ value: "5.5e", label: "5.5e (2024)" },
+	{ value: "pf2e", label: "Pathfinder 2e" },
 ];
 
 const THEME_OPTIONS: {
@@ -36,7 +37,7 @@ export function SettingsModal({ open, onClose }: Readonly<SettingsModalProps>) {
 			<div className="flex flex-col gap-5">
 				<div>
 					<span className="mb-2 block font-medium text-muted-foreground text-sm">
-						Rules Edition
+						Game System
 					</span>
 					<div className="flex gap-1">
 						{EDITION_OPTIONS.map((opt) => (