docs: correct CI/platform documentation that was stale, wrong, or load-bearing

The 2026-09-29 session found the merge gate did not exist -- no branch protection, no
runner -- while the tree asserted both. This corrects the documents that carried, and in
several cases CAUSED, that belief.

CLAUDE.md gains section 2b: never infer platform state from this repository. It carries
the specific API and kubectl checks for protection, runners, CI status, workloads and
Flux revisions, and the rule that a green tick is not proof anything ran (a skipped Gitea
job reports success). This is the rule whose absence produced every other finding.

.gitea/workflows/README.md and merge-gate.yaml both said "there is no remote git host,
this file is dormant". Gitea had been live for weeks. Both were written as plans and never
revisited once the plan completed. The Transition section is now marked COMPLETE and says
what is genuinely still outstanding (CLUSTER_AVAILABLE unset, so L2/L3 never runs in CI).

DECISIONS-LOG 2026-08-31 is annotated IN PLACE. Anyone reading chronologically previously
hit "required status check; runner incluster-dind online" with nothing marking it false
until a month later. The correction now sits on the bullet itself.

ci/README.md, clusters/README.md and both conformance READMEs carry a status banner: they
speak as though no cluster exists, which makes a live L2/L3 coverage gap read as an
expected phase. That framing is why the gap went unexamined.

apps/wave-1/gitea-actions-runner-secret.sops.yaml: fixed a wrong path, replaced advice to
`sops -d` into a terminal (which CLAUDE.md forbids) with the rotation script, and recorded
that a fresh token alone does not re-register a runner holding a stale /data/.runner.

apps/wave-0/plex-claim-secret.sops.yaml: the header claimed the file ships the placeholder.
It has not since the claim -- it holds the spent token, which is inert and deliberately
left in place.

catalog/plex.yaml and the plex secret both asserted a "~4-minute TTL" as fact. It was
uncited, upstream documents no expiry, and it was the basis for a since-disproven claim
that the pipeline was too slow to fit inside it. Measured: ~2m45s.

Both .sops.yaml files were verified to still decrypt after the comment edits
(`sops -d > /dev/null`), and render==golden confirms the catalog comment does not
propagate into the rendered manifest.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

CLAUDE.md

@@ -45,6 +45,35 @@ the toolbox gate yourself and quote its numbers. Never describe a PR as "green"
 strength of a check you have not seen report — and note that a **skipped** Gitea job
 reports as `success`, so a green tick is not by itself evidence that anything ran.
 
+## 2b. Never infer platform state from this repository
+
+**This repo is not evidence about the live platform.** Neither is `DECISIONS-LOG.md`.
+Both describe what someone believed at the time of writing, and both have been
+confidently wrong for a month at a stretch.
+
+On 2026-09-29 the log stated the merge gate was a required status check with a runner
+online. The API said `branch_protections: []` and **zero** runners. Everything downstream
+of that belief — "the gate enforces this", "your push would be rejected", "CI covers it" —
+was wrong, and nothing in the tree could have revealed it, because the tree was the source
+of the error.
+
+**So, before asserting that any gate, protection, runner, secret, or workload is in a
+given state: query the thing itself.**
+
+| Claim about... | Check |
+|---|---|
+| branch protection / required checks | `GET /api/v1/repos/{owner}/{repo}/branches/main` |
+| a runner exists | `GET /api/v1/admin/actions/runners` |
+| CI actually ran | the commit's `/statuses` — and read the **description**; a *skipped* Gitea job reports `success` with "Has been skipped" |
+| a workload / Secret / env | `kubectl --context k3s-prod ...` (read-only is fine for agents) |
+| Flux applied your commit | compare `.status.lastAppliedRevision` against the GitRepository's artifact revision |
+
+Quote the measured field, not the prose. If you cannot measure it, say so explicitly —
+"unverified" is a legitimate report, and a far better one than a confident guess that
+matches the docs.
+
+**A green tick is not proof anything ran.** Read what actually executed.
+
 ## 3. Gate before you push
 
     ./infra/devcontainer/dev.sh run bash -c './ci/gate.sh'