refactor(fts): drop targetConn! assertions, add targetConn-path test

Addresses the adversarial review on PR #726.

- Replaced `targetConn!` non-null assertions in loadFTSExtension with a
  typed local that TypeScript can narrow without `!`.
- Added an integration test exercising loadFTSExtension(conn) on a fresh
  Connection — the path used by the pool adapter but previously only
  covered transitively through search-pool tests.

gitnexus/src/core/lbug/lbug-adapter.ts

@@ -1156,12 +1156,11 @@ export const getEmbeddingTableName = (): string => EMBEDDING_TABLE_NAME;
  */
 export const loadFTSExtension = async (targetConn?: lbug.Connection): Promise<boolean> => {
   const useModuleState = targetConn === undefined;
-  if (useModuleState) {
-    if (ftsLoaded) return true;
-    if (!conn) {
-      throw new Error('LadybugDB not initialized. Call initLbug first.');
-    }
-    targetConn = conn;
+  if (useModuleState && ftsLoaded) return true;
+
+  const c: lbug.Connection | null = targetConn ?? conn;
+  if (!c) {
+    throw new Error('LadybugDB not initialized. Call initLbug first.');
   }
 
   const markLoaded = (): true => {
@@ -1171,13 +1170,13 @@ export const loadFTSExtension = async (targetConn?: lbug.Connection): Promise<bo
 
   try {
     // Try loading locally first (no network required)
-    await targetConn!.query('LOAD EXTENSION fts');
+    await c.query('LOAD EXTENSION fts');
     return markLoaded();
   } catch {
     // Fall back to install + load (requires network)
     try {
-      await targetConn!.query('INSTALL fts');
-      await targetConn!.query('LOAD EXTENSION fts');
+      await c.query('INSTALL fts');
+      await c.query('LOAD EXTENSION fts');
       return markLoaded();
     } catch (err: any) {
       const msg = err?.message || '';

gitnexus/test/integration/lbug-core-adapter.test.ts

@@ -45,6 +45,31 @@ withTestLbugDB(
         ).resolves.toBeUndefined();
       });
 
+      it('loadFTSExtension(conn): loads on an explicit connection and returns true', async () => {
+        const lbug = (await import('@ladybugdb/core')).default;
+        const { loadFTSExtension, getDatabase } =
+          await import('../../src/core/lbug/lbug-adapter.js');
+
+        const db = getDatabase();
+        expect(db).not.toBeNull();
+
+        // Fresh Connection on the same Database — simulates the pool adapter's
+        // path where loadFTSExtension is called with an explicit connection
+        // rather than the module-level singleton.
+        const freshConn = new lbug.Connection(db!);
+        try {
+          const loaded = await loadFTSExtension(freshConn);
+          expect(loaded).toBe(true);
+
+          // Idempotent on the same connection — calling again still returns true
+          // (exercises the "already loaded" catch branch in the fallback path).
+          const loadedAgain = await loadFTSExtension(freshConn);
+          expect(loadedAgain).toBe(true);
+        } finally {
+          await freshConn.close().catch(() => {});
+        }
+      });
+
       it('getLbugStats: returns correct node and edge counts for seeded data', async () => {
         const { getLbugStats } = await import('../../src/core/lbug/lbug-adapter.js');