fix(ci): run tests sequentially to prevent config file race condition

Multiple test files share ~/.mails/config.json via saveConfig/loadConfig.
Bun's parallel test execution causes beforeEach in one file to overwrite
config set by another, leading to flaky failures (e.g. resend_api_key
missing). Also bumps CLI_VERSION to match package.json.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: guo-yu

.github/workflows/release.yml

@@ -67,7 +67,7 @@ jobs:
       - run: bun install
       - run: bun run build
       - run: bun run typecheck
-      - run: bun test test/unit/ test/e2e/flow.test.ts test/e2e/sqlite-search.test.ts
+      - run: bun test --concurrency 1 test/unit/ test/e2e/flow.test.ts test/e2e/sqlite-search.test.ts
 
       - name: Publish mails
         run: npm publish --provenance --access public || true