wip(rm-03): rescue checkpoint of in-flight queue-guard work

CHECKPOINT ONLY — not a deliverable, not reviewed, not complete.

Committed by mos-remediation as TRANSPORT after the authoring seat (coder-mos1) became
unable to act: its context window was exceeded at 102.6%/372k AND its overflow-recovery
path failed ("Turn prefix summarization failed: servers overloaded"). The seat could not
process instructions or commit its own work, leaving 28 modified files durable only on
local disk.

Authorship preserved as coder-mos1 — this is transport, not authorship. The work is the
seat's; committing it is the only way to make it survive the rotation that must follow.

Scope note, unresolved: this diff spans the queue-guard tools (9 files under
framework/tools/git) AND 5 framework guides plus 11 agent templates. RM-03 was scoped to
ci-queue-wait.sh and its tests. Whether the doc/template edits are consequential to the
tri-state change or drive-by was queried and never answered — the seat was bricked before
it could reply. That question stays open and must be resolved before any of this is
reviewed; the wider edits may need splitting out.

Direct instance of D-31: commit-then-rotate works, rotate-without-commit loses everything.

docs/scratchpads/rm-03-queue-guard.md

@@ -0,0 +1,93 @@
+# RM-03 — CI Queue Guard Repair
+
+- **Task:** RM-03
+- **Issue:** #1019
+- **Branch:** `fix/rm-03-queue-guard`
+- **Owner:** coder-mos1
+- **Reviewer:** rev-974 (independent; author != reviewer)
+- **Started:** 2026-08-01
+
+## Objective
+
+Repair the mandatory CI queue guard so it reads provider payloads, blocks asserted non-green CI, distinguishes provider unavailability from a real non-green result, and inspects the branch actually being pushed or merged.
+
+## Constraints
+
+- Worktree only: `/home/hermes/agent-work/rm-03`; never mutate `/src/mosaic-stack`.
+- JSON payload travels through stdin; never argv. Large payload must remain below no ARG_MAX dependency.
+- TDD is mandatory. Every behavior case must be observed red before implementation.
+- No bypass flags or hook suppression.
+- Do not cite the existing guard's green as evidence; D-23 establishes it is zero-information.
+- Gate-ready is a frozen exact head. Any push after a merge-gate verdict voids that verdict.
+- No merge: coordinator holds the merge hand pending Jason.
+
+## Design
+
+1. Feed JSON to `python3 -c` on stdin, including pending-context rendering.
+2. Classify valid green as `READY`; pending/failure/no-status/malformed/mixed as `ASSERTED_NOT_READY`; provider/credential/transport inability as `CANNOT_ASSERT`.
+3. `ASSERTED_NOT_READY` exits nonzero. `CANNOT_ASSERT` emits a loud diagnostic and appends a local JSONL audit record. Push degrades to exit 0; merge holds with distinct retryable exit 75 until provider recovery, then self-clears without manual reset. Inability to write the audit exits nonzero.
+4. Derive the current branch when `-B` is omitted. The merge wrapper passes the exact PR head branch, repository, and full commit SHA—not its `main` base—so fork PRs cannot resolve against an adjacent base-repository branch.
+
+## Test matrix
+
+| Case | Required outcome |
+| --- | --- |
+| success | exit 0; terminal-success |
+| pending | nonzero after bounded timeout |
+| failure | nonzero |
+| no-status | nonzero |
+| malformed | nonzero |
+| >=150 KiB payload | unchanged classification; never rc126 |
+| provider unreachable on push | loud audited CANNOT_ASSERT; degraded exit 0 |
+| provider unreachable on merge | loud audited CANNOT_ASSERT; retryable exit 75/HOLD |
+| audit unavailable | nonzero |
+| implicit push branch | provider URL uses checked-out feature branch |
+| merge wrapper | queue guard receives exact PR head branch/repository/full SHA |
+
+## RED-first evidence
+
+Observed against the unmodified `origin/main` implementation before source edits:
+
+- `bash packages/mosaic/framework/tools/git/test-ci-queue-wait-tristate.sh` → rc 1 with 15 failed assertions.
+- Success payload was reported `state=unknown`.
+- Pending, failure, no-status, and malformed payloads each exited 0 and omitted `ASSERTED_NOT_READY`.
+- The 160 KiB payload produced rc 141 because Python never consumed the pipe; it did not classify success.
+- Provider-unreachable exited 7 with no `CANNOT_ASSERT` audit record.
+- Implicit push queried `/branches/main`, not `/branches/fix/rm-03-fixture`.
+- Audit-unavailable emitted no audit diagnostic.
+- A credential-resolution hard-block mutant was then run before trusting that added case: `credential-unresolvable` returned rc 1 and omitted `CANNOT_ASSERT`; the matrix returned rc 1 with two named assertion failures.
+- Review-blocker controls were observed red: structurally invalid `statuses` string and null-entry payloads each exited 0 as `terminal-success`; unsupported-platform discovery exited 1 without diagnostic or audit (seven named assertion failures total).
+- After the push/merge asymmetry ruling, merge-side provider unavailability was observed red at rc 0; its registered case required distinct retryable rc 75.
+- Aggregate `state=success` with zero contexts was observed red: it exited 0 as `terminal-success`; the registered case requires `no-status`/nonzero.
+- Fork/exact-head controls were observed red: `pr-merge.sh` omitted the fork repository and full SHA, and an ignored-arguments mutant re-resolved through `/branches/` instead of the exact fork commit (two named failures).
+- GitHub check-run-only success/pending/failure were each misclassified as `no-status`; the RED run had five named failures and proved the Checks API was never queried.
+- The first merge-pin control was unrunnable because one `local` declaration referenced a variable before assignment under `set -u`; this was disclosed and corrected rather than counted. The runnable RED then showed Gitea payload `{"Do":"squash"}` lacked `head_commit_id`; a separate GitHub run showed `gh pr merge 123 --squash` lacked `--match-head-commit`.
+- A stale-verdict mutant removed the `--expect-head` comparison and was observed red because a moved head reached the provider merge call.
+- `bash packages/mosaic/framework/tools/git/test-pr-merge-queue-branch.sh` initially returned rc 1; captured call was `--purpose merge -B main -t 900 -i 15`.
+
+Logs remain untracked under the worktree as `.mosaic-test-work-red-*.log` and will not be committed.
+
+## Progress
+
+- [x] Mission, remediation charter, task evidence, board, issue #1019, and superseded PR #1023 read.
+- [x] Isolated worktree created and identity configured coherently.
+- [ ] Mutant tests authored and observed red.
+- [ ] Implementation green.
+- [ ] Baseline and situational gates green.
+- [ ] Independent review clean.
+- [ ] PR CI terminal-green at exact head by full step scan.
+- [ ] Merge-gate verdict issued against frozen head.
+
+## Risks / boundaries
+
+- The local JSONL audit is durable operational evidence but not tamper-resistant against the same UID. RM-03 does not claim otherwise.
+- Push-side audited exit 0 is an explicit owner ruling (Option B), accepted to avoid bricking recovery work; merge-side CANNOT_ASSERT remains retryable exit 75/HOLD. The automated security reviewer continues to flag the deliberate push availability tradeoff.
+- Source/deployed-copy equality is owned by RM-02/D-22; this branch changes repository source and its tests only.
+
+## Test evidence
+
+Pending.
+
+## Final evidence
+
+Pending.