fix(sso): gitea + nextcloud OIDC bootstrap was DEAD CODE — envsubst ate the guard

Both ServiceDefinitions guarded their Keycloak OIDC registration with an UNESCAPED
braced expansion:

    if [ -z "${GITEA_OIDC_CLIENT_SECRET:-}" ]; then      # gitea
    if [ -z "${NEXTCLOUD_OIDC_CLIENT_SECRET:-}" ]; then  # nextcloud, then exit 0

apps-wave-0/1 both declare postBuild.substituteFrom: cluster-vars, and neither name is a
cluster-vars key — so Flux's envsubst substituted them away AT RECONCILE TIME, long
before the container ever ran. Verified in the LIVE cluster: the deployed Deployments
literally contain

    if [ -z "" ]; then

which is always true. The entire OIDC registration block has been skipped on EVERY boot
of both apps.

WHY NOBODY NOTICED: both apps DO have the provider registered — `gitea admin auth list`
shows keycloak/OAuth2/true and `occ user_oidc:provider` shows the keycloak provider.
Those live in each app's own database, persisted from an earlier successful registration.
SSO works today and DECISIONS-LOG is not wrong. But the idempotent re-registration is
dead, so any PVC rebuild, DB restore, or fresh cluster build comes up with NO OIDC and
only the break-glass local admin. A PROD BUILD FROM THIS REPO WOULD SILENTLY HAVE NO SSO
on gitea or nextcloud.

The irony: the surrounding code was hardened twice — see its own comments about a "silent
first-boot RACE", the verify-then-retry loops, the marker files. All of that hardening was
unreachable, because the guard above it always evaluated true.

Not a regression from the recent R-ENV-02 tokenization — introduced 2026-08-27 (8738871).

FIXED AT THE RIGHT SEAM: apps/wave-0/gitea.yaml and apps/wave-1/nextcloud.yaml are
RENDER-GENERATED, so the fix is in catalog/*.yaml and the goldens are regenerated.
Escaped to $${...}, the convention documented in clusters/base/apps-vms.yaml. Post-envsubst
the container now receives the intended `${VAR:-}` instead of `""`.

STRICT MODE WOULD NEVER HAVE CAUGHT THIS. Flux deliberately exempts default-providing
operators (-, :-, +, :+, =, :=, ?, :?) from StrictPostBuildSubstitutions, because they
"intentionally handle the unset case". So a targeted check was required.

MADE UN-REPEATABLE IN THE RENDERER: catalog/render.py gains a substitution-safety section
wired into emit(), so every render path refuses to emit a manifest containing a braced
expansion that is not exactly ${KNOWN_KEY} for a key read LIVE from cluster-vars (no
hardcoded copy to drift; unreadable => empty set => fail-closed). Dollar-runs are counted
properly ($$ is a literal $ to envsubst, so odd runs are flagged and even runs are not),
and indexed forms get their own hard-error message. Nine new --selftest assertions,
including the exact regression. Proven to bite: rendering the pre-fix catalog files from
HEAD now exits 1 with the precise diagnosis.

Sweep: the complete substituted surface was enumerated from every Kustomization's path.
catalog/ contains exactly TWO braced expansions and both were these bugs; every other
braced expansion on a substituted path is a declared cluster-vars key (zero typos, zero
undeclared names); existing $${UOS_URL} escapes verified intact.

Verified: --selftest PASS; canonical render is byte-identical to the committed apps/ for
all 10 onboarded services; the three L1 render checks pass.

NEXT RECONCILE: both pod templates change, so gitea (wave 0) and nextcloud (wave 1) roll —
strategy: Recreate on RWO Longhorn PVCs, so expect a brief single-pod outage each. The
OIDC block then executes for the first time in these apps' deployed lifetime. Both paths
are idempotent (gitea takes auth update-oauth on the existing id; nextcloud's
user_oidc:provider is create-or-update), so the expected result is a no-op re-write plus
the verify loop logging success. If the SOPS client secret ever diverged from Keycloak's,
this is when it gets corrected instead of silently left stale. Tail both pods after merge.

Serves: R-IDP-02, R-IDP-06, R-ENV-02, R-GITOPS-02.

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

catalog/nextcloud.yaml

@@ -111,7 +111,19 @@ lifecycle:
           # every start so it survives pod rolls / PVC rebuilds. Confirmed root cause 2026-08-27.
           OCC config:system:set allow_local_remote_servers --value=true --type=boolean >/dev/null 2>&1 \
             || echo "[nextcloud-oidc] WARN: failed to set allow_local_remote_servers" >&2
-          if [ -z "${NEXTCLOUD_OIDC_CLIENT_SECRET:-}" ]; then
+          # NOTE the `$$` escape below — it is load-bearing. apps-wave-1 declares postBuild.
+          # substituteFrom cluster-vars, so Flux envsubst rewrites this whole manifest at RECONCILE
+          # time, before any container runs. Written unescaped, `$${NEXTCLOUD_OIDC_CLIENT_SECRET:-}` is
+          # not a cluster-var, so envsubst blanked it and the guard reconciled as `[ -z "" ]` — ALWAYS
+          # TRUE — so this hook `exit 0`d here on EVERY boot since 8738871 (2026-08-27), never
+          # installing/enabling user_oidc nor registering the provider. SSO kept working only because
+          # the provider was already in the DB; a PVC rebuild or fresh cluster would have come up with
+          # NO OIDC at all. Flux STRICT substitution cannot catch this — it EXEMPTS default-operator
+          # forms by design. `$${VAR}` is the escape: envsubst emits it back as a plain brace expansion
+          # for the shell. Bare `$VAR` and `$(cmd)` are left alone and need NO escaping — which is why
+          # `--clientsecret-env` and the bare uses below always worked and only the guard broke.
+          # Contract: clusters/base/apps-vms.yaml. Enforced at render time by catalog/render.py.
+          if [ -z "$${NEXTCLOUD_OIDC_CLIENT_SECRET:-}" ]; then
             echo "[nextcloud-oidc] client secret unset; skipping OIDC (break-glass admin only)"
             exit 0
           fi