test(fleet): make stale marker BusyBox-safe (#1043)

docs/scratchpads/1043-pane-git-identity.md

@@ -152,6 +152,46 @@ The PR's `311/311` is correct for its explicitly named six-file command at both
 
 Review 97 reported 312/312 without naming its six files. That is a different or miscounted population and cannot replace the command-scoped 311 denominator; the PR follow-up will name the exact files and arithmetic.
 
+## Round 3 — Alpine stale-marker portability
+
+### Objective and plan
+
+- Replace the GNU-only relative-date fixture with a deterministic POSIX/BusyBox timestamp while preserving the required stale-marker assertion.
+- Re-run the launcher suite in the canonical `ci-base:latest` Alpine image, then run applicable repository gates and independent review.
+- Update the PR body to name the repeated GNU-host/Alpine-CI portability pattern, run the mandatory queue guard, push once, verify provider attribution, and stop without CI polling.
+- Working budget: 8K tokens; scope is one fixture line plus delivery evidence. No production behavior changes.
+
+### RED-first evidence
+
+Before the fix, the canonical CI image command
+`docker run --rm -v "$PWD:/work" -w /work git.mosaicstack.dev/mosaicstack/stack/ci-base:latest bash packages/mosaic/framework/tools/fleet/test-start-agent-session.sh`
+exited 1 at the stale-marker setup with exact BusyBox output
+`touch: invalid date '10 seconds ago'`. The prior fresh-marker assertions had already executed, matching pipeline 2233's failure location.
+
+### Root cause and fix
+
+The test used GNU `touch -d` relative-date parsing although the PR workflow runs on Alpine/BusyBox. The fixture now uses POSIX `touch -t 200001010000.00`, a fixed timestamp that is unconditionally stale; the stale assertion remains mandatory and was not made tolerant of missing timestamp metadata.
+
+### Structural pattern
+
+This is the third GNU-host/Alpine-CI portability defect in the lane: GNU `grep` multi-match counting, Perl-only fixture mutation, and GNU `touch -d` date parsing. The repeated cause is shell suites authored on a GNU host but executed in an Alpine CI image; durable prevention belongs in CI-image execution or portability lint, not assertion weakening.
+
+### GREEN and quality evidence
+
+- Focused launcher suite in `ci-base:latest`: exit 0, `ok - start-agent-session generated environment boundary`.
+- Canonical test step in `ci-base:latest` with the pipeline's `pgvector/pgvector:pg17` service, readiness check, migration, and `pnpm test`: exit 0; 46/46 Turbo tasks; Mosaic 81/81 files and 1510/1510 tests; Gateway 57 passed/5 skipped files and 629 passed/11 skipped tests; enumeration 49 population / 32 enumerated / 18 signed exclusions / 45 named surfaces.
+- The first image-only `pnpm test` attempt lacked the pipeline PostgreSQL service and failed only on connection refusal after the launcher suite was GREEN. The rerun supplied the canonical service precondition and passed.
+- Canonical-image baseline: typecheck 45/45 tasks, lint 25/25 tasks, format check GREEN; `git diff --check` GREEN.
+- Independent Codex code review: APPROVE, confidence 0.96, 2/2 Round-3 files, no findings.
+- Independent Codex security review: risk none, confidence 0.99, 2/2 Round-3 files, no findings.
+
+### Re-derived inventory and denominators
+
+- Round-3 git delta: **2/2 files** — launcher suite and task scratchpad; 25 insertions / 1 deletion before evidence finalization.
+- Full PR path inventory against `origin/main` at `85d2108e`: **19/19 changed paths**; Round 3 adds no new PR path.
+- Workflow definition population: **1/3 pull-request-eligible** (`ci.yml` of `ci.yml`, `ci-image.yml`, `publish.yml`).
+- Do not re-litigate the settled 311/312 populations; both are valid for their separately named Tess6 and CRUD-core7 sets.
+
 ## Residual risk
 
 - Landing on `main` does not update the currently installed host launcher. Host framework installation/reseed and Jarvis live-seat validation are separate downstream events.

packages/mosaic/framework/tools/fleet/test-start-agent-session.sh

@@ -402,7 +402,7 @@ write_generated "$HOME_NATIVE_STALE" "coder-native-stale"
 write_heartbeat_local "$HOME_NATIVE_STALE" "coder-native-stale"
 STALE_HB="$HOME_NATIVE_STALE/run/coder-native-stale.hb"
 printf 'ts=native\npid=1\nstatus=busy\nmodel=stale-model\n' > "$STALE_HB"
-touch -d '10 seconds ago' "$STALE_HB.native"
+touch -t 200001010000.00 "$STALE_HB.native"
 MOSAIC_TEST_PANE_PID=$$ run_start "$HOME_NATIVE_STALE" coder-native-stale
 wait_for_sidecar_status "$STALE_HB"