refactor: migrate VaultTools to use adapter interfaces

Update VaultTools constructor to accept IVaultAdapter and
IMetadataCacheAdapter. Add factory function for production usage.
Update stat, exists, and createFileMetadataWithFrontmatter methods.

src/tools/vault-tools-factory.ts

@@ -0,0 +1,15 @@
+import { App } from 'obsidian';
+import { VaultTools } from './vault-tools';
+import { VaultAdapter } from '../adapters/vault-adapter';
+import { MetadataCacheAdapter } from '../adapters/metadata-adapter';
+
+/**
+ * Factory function to create VaultTools with concrete adapters
+ */
+export function createVaultTools(app: App): VaultTools {
+	return new VaultTools(
+		new VaultAdapter(app.vault),
+		new MetadataCacheAdapter(app.metadataCache),
+		app
+	);
+}