review(5 init): Phase 5 Adversary init — break-it probes + two blocking findings

Break-it probes (V1):
- !testmexyz on custom-html PR#2 (watched repo): correctly ignored — no Drone trigger ✓
- Non-collaborator auth: GET /orgs/recipe-maintainers/members/nonexistent-user-999 → 404 ✓
- bridge source: parse_body("!testmexyz") → (False, False) ✓

CRITICAL finding A5-2 (blocks V2–V8): testme-on-pr.sh reads Gitea commit statuses on the recipe
PR head SHA, but the bridge NEVER posts commit statuses — only PR comments. Drone posts statuses
on cc-ci repo only. POST=0 testme-on-pr.sh custom-html 2 → VERDICT=PENDING always. Fix: bridge
must POST /repos/{owner}/{recipe}/statuses/{sha} on build start/finish.

Finding A5-1: custom-html-tiny not in bridge POLL_REPOS — testme on tiny PRs would silently do
nothing. Must enroll it or use custom-html as sandbox instead.

BUILDER-INBOX.md: heads-up to Builder with both findings.

machine-docs/BACKLOG-5.md

@@ -0,0 +1,61 @@
+# Phase 5 — BACKLOG
+
+SSOT: `/srv/cc-ci/cc-ci-plan/plan-phase5-verify-upgrade-flow.md`. DoD = V1–V9.
+Single-writer: `## Build backlog` = Builder-only; `## Adversary findings` = Adversary-only.
+
+---
+
+## Build backlog
+
+(Builder-owned. Adversary reads but does not write this section.)
+
+---
+
+## Adversary findings
+
+### [adversary] A5-2 — CRITICAL: testme-on-pr.sh cannot read verdicts (commit status vs comment mismatch)
+**Status:** OPEN — Builder must fix before V2–V8 can pass.
+
+`testme-on-pr.sh` reads Gitea commit statuses on the recipe PR's head SHA. But the bridge NEVER
+sets Gitea commit statuses on recipe repos — it only posts PR comments (the YunoHost card+badge).
+Drone posts commit statuses on the `cc-ci` repo (its own repo), not on recipe repos.
+
+**Evidence:**
+- `GET /repos/recipe-maintainers/custom-html/commits/db9a95024e9d.../status` → `state:'', statuses:0`
+- `POST=0 testme-on-pr.sh custom-html 2` → `VERDICT=PENDING BUILD=?` (always, on any known-green PR)
+- Bridge source `bridge.py`: no call to `POST /repos/{owner}/{recipe}/statuses/{sha}` anywhere
+
+**Required fix (one of):**
+1. (Preferred) Bridge: after triggering a Drone build, POST `state=pending` on the recipe PR's head
+   SHA; on build completion, POST `state=success` or `state=failure` with the build URL as
+   `target_url`. This makes `testme-on-pr.sh` work unmodified, adds a native SCM status indicator.
+2. `testme-on-pr.sh`: scan the recipe PR's comments for the `<!-- cc-ci:testme -->` marker and parse
+   the result from the comment body (fragile but avoids bridge changes).
+
+**Repro:** `POST=0 MAX_WAIT=60 INTERVAL=5 /srv/cc-ci/.claude/skills/recipe-upgrade/testme-on-pr.sh custom-html 2`
+→ always `VERDICT=PENDING` even after a green Drone build.
+
+(Only Adversary closes this, after re-testing with a VERDICT=GREEN on a real green build.)
+
+### [adversary] A5-1 — custom-html-tiny not in bridge poll list
+**Status:** OPEN — needs Builder attention or plan clarification.
+
+The Phase 5 plan specifies using `custom-html-tiny` as the sandbox recipe for V3–V8 tests.
+However the bridge's poll list (from live container logs) does NOT include `recipe-maintainers/custom-html-tiny`:
+```
+poller (primary) watching ['recipe-maintainers/cc-ci', 'recipe-maintainers/custom-html',
+'recipe-maintainers/keycloak', 'recipe-maintainers/cryptpad', 'recipe-maintainers/matrix-synapse',
+'recipe-maintainers/lasuite-docs', 'recipe-maintainers/n8n', 'recipe-maintainers/hedgedoc'] every 30s
+```
+
+This means `!testme` on a `custom-html-tiny` PR will NOT trigger a Drone build. Either:
+1. The builder must add `custom-html-tiny` to the bridge's enrolled repos list (and enroll its tests), OR
+2. Use `custom-html` (which IS enrolled) as the sandbox recipe instead, OR
+3. The plan's V3–V8 tests must first enroll the sandbox recipe as part of Phase 5 setup
+
+**Repro:** `docker logs ccci-bridge_app.1.<id> 2>&1 | head -3` on cc-ci shows the poll list.
+
+**Impact:** V3, V4, V5, V8 tests using `custom-html-tiny` as sandbox will fail silently (the `!testme`
+comment is posted but the bridge never sees it → VERDICT stays PENDING forever).
+
+(Only Adversary closes this after re-test.)