fix(runbooks): declare whole-repo scope, drop the bespoke l0 stage, +cnpg-primary-spread

Three corrections after rebasing onto main.

1. THE GUARD CAUGHT A REAL ONE ON ITS FIRST CONTACT WITH main. main had gained
   `CNPGPrimariesCoLocated` (platform/cnpg/alerts.yaml) pointing at
   /runbooks/cnpg-primary-spread, with no runbook. The check failed the rebase exactly as
   designed — 46 annotations, 35 names, 34 present — naming both the missing file AND the
   missing configMapGenerator entry. runbooks/cnpg-primary-spread.md now exists: what
   co-located primaries actually cost here (blast radius, not an outage, because
   instances: 3 + required anti-affinity), why the drift is uncorrectable-by-declaration
   (CNPG has no primary-placement field), the readiness gate that keeps the rule quiet
   during a real node outage, and the ~9s-per-database switchover rebalance, one cluster
   at a time. The 2026-09-07 outage in which all three primaries sat on one node is the
   reason the alert exists at all.

2. WHOLE-REPO SCOPE, NOT A HAND-WRITTEN STAGE. main's refactor replaced ci/l0.sh's
   per-check "UNCONDITIONAL" stages with a declaration:
   `conformance.home.k3s/scope: "whole-repo"`, unioned into every gate run by Stage 3b's
   `--include-scope`. My +38-line Stage 3f is removed (ci/l0.sh is now byte-identical to
   main) and the annotation is declared instead. Assertion (7) of the check was rewritten
   to match: it no longer asserts its own path appears in ci/l0.sh — it asserts the test
   DECLARES the scope and that ci/l0.sh still passes --include-scope, since neither half
   alone makes the check load-bearing. That matters here because
   ci/touched-requirements.sh maps platform/monitoring/* to "R-OBS-01 R-OBS-02", not
   R-OBS-04, and maps platform/kubevirt/* and runbooks/* to nothing at all.

3. A FACTUAL CORRECTION IN ALL 35 RUNBOOKS. Every page claimed `dev.sh` defaults its
   current-context to k3s-dev. main's `9b4744d fix(devcontainer): dev.sh defaults to
   prod` made that false, and a runbook that misstates which cluster a command talks to is
   worse than one that says nothing. The pages now say what is durably true: the default
   has already changed once, so naming `--context k3s-prod` is what makes a command mean
   the same thing next month, and the per-invocation banner is there to be read. The
   check's own failure message was corrected the same way.

Re-verified after all three: check green at 374 assertions (46 annotations, 35/35 runbooks
present, 35/35 projected), re-applied to prod, and re-probed in-cluster through the
Gateway — node-down, keycloak-down, keycloak-client-secrets, cnpg-archiving,
longhorn-faulted, vpn-down, node-io and cnpg-primary-spread all HTTP 200 with
text/plain; charset=utf-8 and 8.9-12.1 KB of real body; /runbooks/ index 200; an unknown
name 404s with a pointer rather than a blank page; and homepage still answers the apex `/`,
confirming Gateway API longest-path precedence.

Full merge gate: PASS (spec-immutability, lint, l0, render-golden, l1 all green;
prom-rules SKIPPED for want of promtool in the image; L2/L3 SKIPPED, no cluster).

Co-Authored-By: Claude Opus 5 <[email protected]>

runbooks/node-cpu.md

@@ -31,10 +31,14 @@ that hang is not the cluster being down. Every command below runs as:
 
     infra/devcontainer/dev.sh run bash -c 'kubectl --context k3s-prod get nodes'
 
-Always pass `--context k3s-prod` explicitly. `dev.sh` merges both clusters into one kubeconfig and
-defaults its current-context to k3s-**dev**, so a command without `--context` silently answers
-about the wrong cluster. (`CLUSTER=prod infra/devcontainer/dev.sh run kubectl ...` is equivalent.)
-Do not run two `dev.sh` invocations at once — they share one container and interfere.
+Always pass `--context k3s-prod` explicitly. `dev.sh` merges BOTH clusters into one kubeconfig and
+picks a current-context per invocation, and **that default has already changed once** — it was k3s-dev
+until dev was decommissioned on 2026-09-13, and is k3s-prod now. A command that names its context means
+the same thing next month as it does today; one that relies on the default does not, and the failure is
+silent (it answers confidently about the other cluster). `CLUSTER=prod infra/devcontainer/dev.sh run
+kubectl ...` selects it explicitly, and every invocation prints a banner naming the cluster it is about
+to talk to — read it. Do not run two `dev.sh` invocations at once; they share one container and
+interfere.
 
 USE FULLY-QUALIFIED RESOURCE NAMES, ALWAYS. Three CRDs on this cluster register the kind `Backup`:
 `longhorn.io/v1beta2`, `postgresql.cnpg.io/v1` and `velero.io/v1`. The bare short name resolves to