Fix flaky test gate

The merge lane saw `gate` fail and then pass on a rerun of the same tree. - Test: `gate` - Tree: `16f5b2fe99d1af5cbda507d5ff9e97f5e4be212b` - Lane task: 11920 - Flake record: 01a192ca-3d33-7499-be9d-92d5dadeb1f0 Make it deterministic; do not delete it unless it tests nothing.

Fixed the gate flake: the jaahd forge fixture hit EADDRINUSE binding 127.0.0.2 at a port picked as free only on 127.0.0.1; it now redraws the port. Forced-collision repro: old fixture 3 errors, new one passes. Quick gate green. PR #7517 queued to the lane. Memory: none applied.