Fix transaction test crashing on db/index.ts import

The test imports db/index.ts which eagerly calls postgres() and drizzle()
at the top level. In CI, the dummy DATABASE_URL produces a client without
options.parsers/serializers, crashing drizzle's construct(). Mock both
postgres and @codebuff/internal/env before importing to avoid the real
db initialization — the test only ever spies on db.transaction anyway.

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

Author: jahooma

packages/internal/src/db/__tests__/transaction.test.ts

@@ -3,14 +3,25 @@ import { AnalyticsEvent } from '@codebuff/common/constants/analytics-events'
 import { createPostgresError } from '@codebuff/common/testing/errors'
 import { afterEach, beforeEach, describe, expect, it, mock, spyOn } from 'bun:test'
 
-import * as dbModule from '../index'
-import {
-  getRetryableErrorDescription,
-  isRetryablePostgresError,
-} from '../transaction'
-
 import type { Logger } from '@codebuff/common/types/contracts/logger'
 
+// Mock postgres and env before any module that imports db/index.ts is loaded.
+// db/index.ts calls postgres(env.DATABASE_URL) and drizzle() at the top level,
+// which fails without real env vars / DB. These tests only need db.transaction (spied).
+mock.module('postgres', () => ({
+  default: () => ({
+    options: { parsers: {}, serializers: {} },
+  }),
+}))
+mock.module('@codebuff/internal/env', () => ({
+  env: { DATABASE_URL: 'postgres://mock:mock@localhost:5432/mock' },
+}))
+
+// Now safe to import modules that depend on db/index.ts
+const dbModule = await import('../index')
+const { getRetryableErrorDescription, isRetryablePostgresError } =
+  await import('../transaction')
+
 describe('transaction error handling', () => {
   describe('getRetryableErrorDescription', () => {
     describe('Class 40 — Transaction Rollback errors', () => {