feat: add archeflow-rollback.sh for post-merge test failure auto-revert

skills/git-integration/SKILL.md

@@ -219,6 +219,32 @@ The helper script reads this config if it exists. All values have sensible defau
 
 ---
 
+## Post-Merge Rollback
+
+After merging, the run skill validates the merge by running the project's test suite. If tests fail, the merge is automatically reverted.
+
+### Script
+
+```bash
+./lib/archeflow-rollback.sh <run_id> [--test-cmd <cmd>]
+```
+
+**Behavior:**
+1. Reads `test_command` from `.archeflow/config.yaml` (or uses `--test-cmd` override)
+2. Runs the test suite with a 5-minute timeout
+3. If tests pass: exits 0 (merge is good)
+4. If tests fail: runs `git revert --no-edit HEAD`, emits a `decision` event, exits 1
+5. Verifies HEAD is an ArcheFlow merge commit before reverting (warning if not, proceeds anyway)
+
+**Integration with run skill:** Called in section 4c (All Approved) after `archeflow-git.sh merge`. If it returns non-zero, the orchestrator cycles back with "integration test failure" feedback or reports to the user if max cycles are reached.
+
+**Configuration:** Set `test_command` in `.archeflow/config.yaml`:
+```yaml
+test_command: "npm test"       # or "pytest", "cargo test", etc.
+```
+
+---
+
 ## Safety Rules
 
 These rules are inherited from `archeflow:orchestration` and reinforced here: