refactor: split modern.ts into focused sub-modules

- Extract ai, kiku, lapis, proxy, tags, fields, media, behavior, metadata into own files
- Move applyAnkiKikuResolution import to kiku.ts
- Fix nPlusOne migration: later invalid duplicate values now correctly supersede earlier valid ones

src/config/resolve/anki-connect/modern-metadata.ts

@@ -0,0 +1,22 @@
+import { DEFAULT_CONFIG } from '../../definitions';
+import type { ResolveContext } from '../context';
+import { asString } from '../shared';
+import { applyModernValue } from './modern-value';
+
+export function applyModernMetadataResolution(
+  context: ResolveContext,
+  metadata: Record<string, unknown>,
+): void {
+  applyModernValue(
+    context,
+    metadata,
+    'pattern',
+    'ankiConnect.metadata.pattern',
+    asString,
+    DEFAULT_CONFIG.ankiConnect.metadata.pattern,
+    (value) => {
+      context.resolved.ankiConnect.metadata.pattern = value;
+    },
+    'Expected string.',
+  );
+}