docs(ci): close out the hardening -- land the scripts, correct a claim that shipped wrong

The branch-protection + PR-gate + sidecar sequence is complete and verified. This records
the finished state and fixes what the sequence itself proved wrong.

CORRECTS A FALSE CLAIM I SHIPPED. PR #7 said the sidecar conversion would remove the
one-per-start dockerd line "http: TLS handshake error from 127.0.0.1: EOF". It does NOT.
Exactly one still appears, immediately after "API listen on [::]:2376" -- it is now the
startupProbe's FIRST attempt, landing microseconds after dockerd begins listening and cut
off by timeoutSeconds: 1; the next poll succeeds. Cosmetic, and deliberately not chased:
raising the timeout to hide one benign startup line would slow every subsequent poll. The
manifest comment now states this instead of the wrong prediction.

Lands infra/gitea/require-gate.sh and verify-then-enforce.sh, which drove the rollout from
a session temp dir. verify-then-enforce.sh merges nothing -- merging is a human's reviewed
act -- but forces the reconcile and ABORTS unless the pod is healthy, a runner is online,
and a real workflow goes green on it, before enabling enforcement and probing the push.
Re-run it after any future act-runner change.

Trims the now-obsolete feat/ rationale from claim-ship.sh: per-branch push triggers were
deleted, so no prefix produces a duplicate run any more.

CLAUDE.md's enforcement table flips from "weaker than this rule" to machine-enforced, with
all four rows marked verified and the push rejection noted as PROVOKED rather than assumed.
It also now states what a green PR does NOT prove: CLUSTER_AVAILABLE is unset, so L2/L3
never runs in CI and only the L0/L1 offline subset is covered.

infra/gitea/README.md marks the sequence done and names the root cause that remains
unfixed: Gitea repo settings live in its own database, invisible to Flux and unreadable by
the conformance gate, so NOTHING detects drift from what this directory declares. These
scripts assert desired state; they are not a detector. The check that reads the live API
and fails on divergence is the highest-value work left, and it is the difference between
this being fixed and this being unable to recur.

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

infra/plex/claim-ship.sh

@@ -26,9 +26,10 @@ creds="$(printf 'protocol=https\nhost=%s\n\n' "$HOST" | git credential fill)"
 U="$(sed -n 's/^username=//p' <<<"$creds")"; P="$(sed -n 's/^password=//p' <<<"$creds")"
 api() { curl -sS --config <(printf 'user = "%s:%s"\n' "$U" "$P") "$@"; }
 
-# feat/ prefix ON PURPOSE. act_runner capacity is 1, and gate.yml's PUSH trigger covers
-# feature/** fix/** docs/** chore/** but NOT feat/** — so a chore/ branch would fire a
-# second, redundant run that SERIALISES ahead of the PR run and doubles the wall clock.
+# Branch prefix is now cosmetic. It used to matter: gate.yml's push trigger covered
+# feature/** fix/** docs/** chore/** but not feat/**, and with act_runner at capacity 1 a
+# matching prefix fired a redundant run that serialised ahead of the PR run. Those
+# per-branch push triggers were deleted, so no prefix produces a duplicate run any more.
 BRANCH="feat/plex-claim-token-$(date +%H%M%S)"
 
 el "committing on $BRANCH"