docs(TST-30): document shared-runner CI bottleneck + second-runner operator runbook

Doc half of TST-30 (single shared Gitea runner is a CI throughput/availability
bottleneck): docs/GatewayTesting.md's Continuous Integration section gains a
"Runner capacity is shared and finite" subsection covering the maxParallel=1
instance-level runner shared with dohertj2/lmxopcua, the ~20-30 min queue
latency observed under cross-repo contention, and Gitea 1.26's missing run
cancel/delete API. The existing "windev tier down" degraded-mode paragraph now
also covers "runner contended" as a reason to bypass the queue via
CI_SHA=<sha> scripts/ci/run-windev-ci.sh <mode> or the manual windev worktree
flow, generalizing it per the finding's design note.

New operator runbook docs/runbooks/TST-30-second-ci-runner.md carries the
actual runner registration (option a: second act_runner instance on
10.100.0.35 with the same container.network: traefik config, recommended;
option b: dedicated labelled runner, escalation only; option c: runner on
windev, rejected) plus verification steps and the no-cancel caveat. The
optional workflow-level concurrency group is documented as unverified --
framed as "verify before relying on it" -- and left unimplemented in ci.yml,
since registering the runner and any runs-on gating is operator/infra work
outside this repo's tree.

Tracking: TST-30 -> Done (doc half; runner registration operator-pending) in
both registers + change-log row.

archreview/2026-07-12/remediation/60-testing-docs-gaps.md

@@ -15,7 +15,7 @@ Prior-cycle open findings (TST-05..24 where still open) are tracked in the prior
 | TST-27 | Medium | P1 (doc batch) | S | — | Done | `ShowTagValues` config row still says "Reserved" after SEC-25 made the flag live |
 | TST-28 | Low | P2 | S | relates IPC-02 | Done | Gateway-side `max_frame_bytes` handshake field untested in the CI-run suite |
 | TST-29 | Low | P2 | S | — | Done | Retire `oldtasks.md` after folding the Phase-5 governance record into DesignDecisions.md; delete root docs-review artifacts |
-| TST-30 | Low | P2 | M | — | Not started | Single shared Gitea runner is a CI throughput/availability bottleneck (cross-repo contention, no run cancel/delete) |
+| TST-30 | Low | P2 | M | — | Done (doc half; runner registration operator-pending per runbook) | Single shared Gitea runner is a CI throughput/availability bottleneck (cross-repo contention, no run cancel/delete) |
 
 ---
 
@@ -167,6 +167,8 @@ Independent of the runner count, document the **no-cancel** reality (Gitea 1.26
 
 **Verification.** Push two branches back-to-back and confirm their runs execute concurrently (not serially) once a second runner exists; `GET /repos/dohertj2/mxaccessgw/actions/runners` (or the instance runner list) shows ≥2 runners online; `docs/GatewayTesting.md` describes the shared-runner/no-cancel reality and the bypass. Re-run the TST-25 acceptance push and confirm queue depth is materially lower under a concurrent `lmxopcua` run.
 
+**Outcome (2026-08-07 — Done, doc half; runner registration operator-pending).** Landed on `fix/tst-30-runner-docs`. Implementation step 2 shipped: `docs/GatewayTesting.md`'s Continuous Integration section gained a "Runner capacity is shared and finite" subsection stating the `maxParallel=1` co-located runner is shared with `dohertj2/lmxopcua` at the instance level (not repo-scoped), the ~20–30 minute queue latency observed under cross-repo contention, and the Gitea 1.26 no-cancel/no-delete API reality; the existing "windev tier down" degraded-mode paragraph now also covers "runner contended" as a reason to use the bypass, generalized per this finding's design note. New operator runbook `docs/runbooks/TST-30-second-ci-runner.md` carries **step 1** (register a second `act_runner` on `10.100.0.35`, option (a) recommended, same `container.network: traefik` config; option (b) dedicated labelled runner as an escalation; option (c) windev-hosted runner rejected) with the verification checklist (concurrent back-to-back pushes, `GET /repos/dohertj2/mxaccessgw/actions/runners` ≥ 2) and a note that the no-cancel reality persists regardless of runner count. **Step 3 (optional workflow-level `concurrency` group)** is documented in the runbook as unverified — explicitly framed as "verify this Gitea deployment honors it before relying on it" — and left unimplemented in `ci.yml`, since it is a `ci.yml` change out of scope for this doc-only pass. **The actual runner registration (step 1) is infrastructure work outside this repo's tree and remains the operator's to execute**, tracked in the runbook. Verification performed: `grep -n 'maxParallel\|shared\|cancel' docs/GatewayTesting.md` shows the new prose; runbook file exists at the path above; no build required (doc-only change).
+
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 ## Cross-domain dependencies