#23055: test: clear gateway env vars in beforeEach to prevent leakage

Add beforeEach hooks in these test files to ensure a clean environment: - src/gateway/server-runtime-config.test.ts - src/browser/server.post-tabs-open-profile-unknown-returns-404.test.ts This prevents OPENCLAW_GATEWAY_TOKEN and OPENCLAW_GATEWAY_PASSWORD from the outer environment from interfering with auth-related test expectations, making tests deterministic and reliable. <!-- greptile_comment --> <h3>Greptile Summary</h3> Added `beforeEach` hooks to clear `OPENCLAW_GATEWAY_TOKEN` and `OPENCLAW_GATEWAY_PASSWORD` environment variables in two test files to prevent environment leakage. - `src/gateway/server-runtime-config.test.ts`: properly imports `beforeEach` from vitest and clears env vars to ensure auth-related tests run with predictable state - `src/browser/server.post-tabs-open-profile-unknown-returns-404.test.ts`: adds redundant env cleanup in first describe block (already handled by `installBrowserControlServerHooks()`), and the second describe block (`profile CRUD endpoints`) still lacks proper env var cleanup/restoration <h3>Confidence Score: 3/5</h3> - safe to merge but with minor issues that should be addressed - the change properly addresses env var leakage in `server-runtime-config.test.ts`, but has redundant cleanup in one test file and incomplete cleanup in another describe block that could still allow env var leakage - pay attention to `src/browser/server.post-tabs-open-profile-unknown-returns-404.test.ts` - the second describe block needs env var cleanup _{Last reviewed commit: 874a422} <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->