plane(1.5): placement probe -- Substrate places by any free worker, not by fit

ops/ax/probe-placement.sh scales ousast-pool to one worker, applies probe-pool
(1 x 2 CPU / 3Gi, the already-built ateom-gvisor image, no ko build), runs one
model-free repo-facts Task requesting 2560Mi (limit 3Gi) and one requesting
256Mi, records `kubectl ate get workers -o json` after each resume, and removes
everything it created. Live on kind: both actors landed on the 1536Mi
ousast-pool worker (status.allocated.actors=1 there, 0 on probe-pool) ->
placement: any. design.md section 4 records the outcome and the fallback group
5 must take (an engine atespace with engine-pool as its only pool if Substrate
scopes pools by atespace; else a plain Kubernetes Job on k3s). Evidence under
benchmarks/measurements/2026-10-02-k8s-01-profile/probe/.

Gates (tree identical to 1.4 in src/ and tests/; ops/ gains the probe script,
which the literal scan covers): pytest 2010 passed, 42 skipped, exit 0; ruff
check 0; ruff format 0; mypy 0.

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01EmM1j46qgKMh3zqD1QMwEo

.kiro/specs/plane-on-kubernetes/design.md

@@ -254,6 +254,13 @@ containerd; `Dockerfile:1-7` already argues against it).
   a 3 Gi actor lands only on `engine-pool`. If Substrate does not place by resource fit, the fallback is a
   separate atespace with its own pool if Substrate scopes pools that way; failing that, the engine stays
   `alerts-engine` on a Docker host and the k3s engine becomes a plain Kubernetes Job outside ax, recorded as such.
+  **Probe outcome (task 1.5, 2026-10-02, `benchmarks/measurements/2026-10-02-k8s-01-profile/`): `placement: any`.**
+  With `ousast-pool` at one 1536Mi worker and a `probe-pool` of one 3Gi worker both ACTIVE, a `repo-facts` actor
+  requesting 2560Mi (limit 3Gi) was placed on the 1536Mi `ousast-pool` worker (`kubectl ate get workers`: ACTORS
+  1/1000 there, 0/1000 on `probe-pool`), and so was the 256Mi actor. Substrate does not place by resource fit, so
+  group 5 takes the fallback: the engine pool must be the only pool its actors can land on. Before 5.2, check whether
+  Substrate scopes pools by atespace (an `engine` atespace with `engine-pool` as its only pool); if it does not, the
+  k3s engine runs as a plain Kubernetes Job outside ax and `alerts-engine` stays the kind path.
 - **`alerts-engine` stays** for development on a host with Docker (kind profile), its help text and
   `docs/plane.md` row marked "development only; the plane task is `engine`" (Req 4.3). Generated Runs choose
   `engine` when the profile's `images` file has an engine image, else leave `alerts` for `alerts-engine`.

.kiro/specs/plane-on-kubernetes/tasks.md

@@ -42,7 +42,7 @@ go-ahead** with a ceiling; steps that need a hand on a cluster that does not exi
     `runner-image`; `generate.repin_templates` accepts that file (runner key only until task 4.3).
   - Evidence: `ops/ax/up.sh` reruns idempotently on kind; `ops/ax/smoke-run.sh` passes.
   - _Requirements: 1.1, 2.4_
-- [ ] 1.5 Placement probe (open question 2, decided before the engine work)
+- [x] 1.5 Placement probe (open question 2, decided before the engine work) -- result: `placement: any`
   - `ops/ax/probe-placement.sh`: applies a second WorkerPool `probe-pool` (1 replica, 3 Gi) from the design's
     engine template, then one model-free `repo-facts` Task with `resources.requests.memory: 2560Mi`, and records
     with `kubectl ate get workers` which worker took the actor; then the same Task with 256Mi. Removed after.