refactor(core): replace CommonJS requires with named imports (#31)

packages/core/src/indexer.ts

@@ -1,6 +1,7 @@
 // Passive-pull indexing orchestration for the Core package.
+import { existsSync } from 'node:fs';
 import { DB_PATH, openDb, openReadDb, openWriterLeaseDb, rebuildMemoryFts } from './db.ts';
-import { fs, inferProjectPath } from './parsing.ts';
+import { inferProjectPath } from './parsing.ts';
 import {
   createProviderIndexPlan,
   indexProviderPlan,
@@ -67,7 +68,7 @@ function isMissingIndexStateTable(error: unknown): boolean {
 }
 
 function inspectBuildOwnership({ force = false }: { force?: boolean } = {}) {
-  if (!fs.existsSync(DB_PATH)) return { skip: false };
+  if (!existsSync(DB_PATH)) return { skip: false };
   const db = openReadDb();
   try {
     return shouldSkipBuild(db, { ignoreRecentBuild: force });