#4405 Flaky test: serve_upstream_lock_test 'a machine's writes and serve's own runs on one behavior exclude each other' hits a serve request timeout under full-suite load

In verify-build run 50aab89d-0905-4b65-898b-7ee60ef0b347 (commit 1fe61cd, a test-only change in yaml_output_repository_test.ts), this test failed. The run was concurrent with verify-reviews and verify-skills:

integration/serve_upstream_lock_test.ts:201, serve upstream locks: a machine's writes and serve's own runs on one behavior exclude each other

The assertion at line 218 expected no warnings, but got: Swamp lost its connection to serve at http://127.0.0.1:43279 (The operation was aborted due to timeout) after the request may have reached it... The test took 1m14s.

The same test passed in run c8b6dc2a-ec53-4fc2-8f8f-305250bb9730 on the parent commit, which differs only by a test comment and a local rename. The client's request timeout to the in-process serve looks too tight for a contended full-suite run.