Fix all linter errors

- Remove unused biome suppression comment in completions.ts
- Remove unnecessary if condition in execute-bootstrap.test.ts
- Add eslint-disable comments for any type assertions in client.test.ts
- Add eslint-disable comments for expect().rejects patterns
- Fix template literal number expression with toString()
- Fix error handling in test-db.ts to avoid object stringify

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/testing/test-helpers/src/test-db.ts

@@ -202,9 +202,11 @@ export async function runMigrations(): Promise<void> {
     await client.query(schemaSql);
   } catch (error) {
     // Ignore "already exists" errors - schema may have already been applied
-    const message = error instanceof Error ? error.message : String(error);
+    const message = error instanceof Error ? error.message : "Unknown error";
     if (!message.includes("already exists")) {
-      throw new Error(`Schema application failed: ${message}`);
+      throw error instanceof Error
+        ? error
+        : new Error(`Schema application failed: ${message}`);
     }
   } finally {
     await client.end();