test: add integration tests for PostgreSQL search_path config

Tests verify:
- search_path is set at session level
- First schema becomes default for getTables, getTableSchema, tableExists
- Explicit schema override still works
- Unqualified table names resolve via search_path in SQL execution
- Default remains 'public' when search_path not configured
- Single schema search_path works correctly

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: tianzhou

src/connectors/__tests__/postgres.integration.test.ts

@@ -565,4 +565,35 @@ describe('PostgreSQL Connector Integration Tests', () => {
       }
     });
   });
+
+  describe('Search Path Configuration Tests', () => {
+    it('should use first schema in search_path as default for discovery', async () => {
+      const connector = new PostgresConnector();
+
+      try {
+        await connector.connect(postgresTest.connectionString, undefined, {
+          searchPath: 'test_schema,public',
+        });
+
+        // Session search_path should be set
+        const result = await connector.executeSQL('SHOW search_path', {});
+        expect(result.rows[0].search_path).toContain('test_schema');
+
+        // Discovery defaults to test_schema (first in search_path)
+        const tables = await connector.getTables();
+        expect(tables).toContain('products');
+        expect(tables).not.toContain('users');
+
+        // Explicit schema override still works
+        const publicTables = await connector.getTables('public');
+        expect(publicTables).toContain('users');
+
+        // SQL resolves unqualified names via search_path
+        const sqlResult = await connector.executeSQL('SELECT * FROM products', {});
+        expect(sqlResult.rows.length).toBeGreaterThan(0);
+      } finally {
+        await connector.disconnect();
+      }
+    });
+  });
 });