feat: add test-first validation gate in Do phase

skills/run/SKILL.md

@@ -245,6 +245,28 @@ After Maker returns:
 
 **Critical:** Verify the Maker committed its changes before proceeding. If uncommitted changes exist, instruct the Maker to commit.
 
+#### 2a-ii. Test-First Validation
+
+After Maker completes, check `do-maker-files.txt` for test files:
+```bash
+TEST_FILES=$(grep -iE '(test|spec)' ".archeflow/artifacts/${RUN_ID}/do-maker-files.txt" || true)
+```
+
+If `TEST_FILES` is empty and domain is not `writing`:
+1. Check if `plan-creator.md` contains a `### Test Strategy` section
+2. If yes: re-run Maker with targeted test instruction (one retry within Do phase)
+3. If no test strategy specified: emit WARNING event and proceed
+
+```bash
+./lib/archeflow-event.sh "$RUN_ID" decision do "" \
+  '{"what":"test_first_gate","chosen":"<pass|warn|retry>","rationale":"<reason>"}' "$SEQ_MAKER_COMPLETE"
+```
+
+The re-run prompt for the retry case:
+> "The proposal specified these test cases: <test strategy section>. No test files were found in your changes. Add the specified tests before finishing."
+
+This is one retry within the Do phase, not a full PDCA cycle. If the retry also produces no tests, emit WARNING and proceed to Check.
+
 #### 2b. Phase Transition: Do to Check
 
 ```bash