Build MVP: campaigns, characters, combat, dice, compendium

- Rules abstraction (5e + pf2e) behind one interface, fully tested
- Pure combat engine: turn-order safe across add/remove/reorder/init-change
- Dexie storage with real cascade deletes + Zod validation on write
- Seedable dice engine with notation parser
- Lazy SRD compendium (code-split), bestiary -> combat
- Strict TS, 54 unit tests, Playwright e2e smoke (all green)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/ui/NumberField.tsx

@@ -0,0 +1,41 @@
+import { cn } from '@/lib/cn';
+
+/** Integer input that never emits NaN — coerces blanks/garbage to a fallback. */
+export function NumberField({
+  value,
+  onChange,
+  min,
+  max,
+  className,
+  'aria-label': ariaLabel,
+}: {
+  value: number;
+  onChange: (n: number) => void;
+  min?: number;
+  max?: number;
+  className?: string;
+  'aria-label'?: string;
+}) {
+  return (
+    <input
+      type="number"
+      inputMode="numeric"
+      aria-label={ariaLabel}
+      value={Number.isFinite(value) ? value : 0}
+      min={min}
+      max={max}
+      onChange={(e) => {
+        const raw = Number(e.target.value);
+        let n = Number.isFinite(raw) ? Math.trunc(raw) : 0;
+        if (min !== undefined) n = Math.max(min, n);
+        if (max !== undefined) n = Math.min(max, n);
+        onChange(n);
+      }}
+      className={cn(
+        'w-full rounded-md border border-line bg-surface px-2 py-1.5 text-center text-sm text-ink',
+        'focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-accent/60',
+        className,
+      )}
+    />
+  );
+}