Test report — board #686 start load gate

Implementation commit under test: f5960be347479d58608206ea1c761bc0ffa4c9dc

Scope

- The default one-minute load threshold is 4 x detected CPUs. Memory and load
  remain independent admission guards.
- Blocked status distinguishes memory, load, both, and an unreadable resource
  probe. START_GATE_WAITING_STATUS remains the compatibility alias for memory.
- Admission completion restores the pre-gate status for all four resource wait
  texts and the single-lane text, while preserving a concurrent unrelated status.
- The agent-node and anet copies are byte-identical.
- ANET_START_GATE_MAX_WAIT_SEC=600 still means transition to single-lane
  admission, not a total wait limit.
- This change does not pass through the database.

Docker results (all containers ran with --cpus=2)

1. test612-start-admission, 512 MiB cgroup: rc=0.
   - real cgroup admission and 14-start single-lane pressure passed;
   - 16 processes with distinct node ids: OVERLAPS=0;
   - 16 processes with one shared node id: OVERLAPS=0;
   - stalled-count and re-entry race witnesses passed;
   - the 10-06 incident sample (16 CPUs, load1 146, 307 MiB available) was
     classified as waiting for both memory and load;
   - changing 4x back to 2x, deleting the memory check, mapping load to the
     memory status, restoring only memory-wait status, deleting the pre-lease
     ownership recheck, and deleting the re-entry cancellation each produced
     the intended assertion failure. The restore mutation failed specifically
     because the load-wait text was no longer recognized.
2. test725-agent-node-unit-ci: rc=0.
   - 2571 pass, 1 skip, 0 fail; 9013 expectations across 195/195 source test
     files; agent-node/tests 6/6; its witnessed-red mutation passed.
3. test798-server-unit-ci (SQLite): rc=0.
   - 204/204 files, 0 failed; password-floor mutation red; RESULT: PASS.
4. test2123-hub-postgres-ladder (PostgreSQL): rc=0.
   - PG adapter/features/migration checks passed; ladder level=6, floor=6;
     RESULT: PASS.

Static gates

- check-doc-symbol-pins: rc=0 (0 drift).
- check-doc-source-pins: rc=0 (0 broken pins).
- check-test-suite-registration: rc=0 (0 new orphan suites).
- git diff --check and byte comparison: rc=0.

No production Hub, node, tmux server, or host load generator was used.
