feat: flesh out check-phase with parallel reviewer spawning protocol

skills/check-phase/SKILL.md

@@ -76,6 +76,107 @@ Use the higher severity. Don't double-count in the verdict.
 → Build cycle feedback (see orchestration skill) and feed to Plan phase
 ```
 
+## Reviewer Spawning Protocol
+
+This section defines the exact sequence for spawning reviewers in the Check phase.
+
+### Step 1: Guardian First (mandatory)
+
+Guardian always runs first, before any other reviewer. It receives the Maker's git diff and the proposal's risk section only.
+
+**Context for Guardian:**
+- `git diff main...<maker-branch>` (the actual code changes)
+- Risk section from `plan-creator.md` (if present)
+- Do NOT include: Explorer research, full proposal, other reviewer outputs
+
+```
+Agent(
+  description: "Guardian: security and risk review for <task>",
+  prompt: "You are the GUARDIAN archetype.
+    Review the diff: <maker's diff>
+    Proposal risks: <risk section from plan-creator.md>
+    Assess: security vulnerabilities, reliability risks, breaking changes, dependency risks.
+    Output: APPROVED or REJECTED with findings in the standardized format.
+    Each finding: | Location | Severity | Category | Description | Fix |",
+  model: <resolve_model guardian $WORKFLOW>
+)
+```
+
+Save output to `.archeflow/artifacts/${RUN_ID}/check-guardian.md`.
+
+### Step 2: A2 Fast-Path Evaluation
+
+After Guardian completes, parse its output before spawning other reviewers:
+
+```bash
+CRITICAL_COUNT=$(grep -ci "CRITICAL" ".archeflow/artifacts/${RUN_ID}/check-guardian.md" || echo 0)
+WARNING_COUNT=$(grep -ci "WARNING" ".archeflow/artifacts/${RUN_ID}/check-guardian.md" || echo 0)
+
+if [[ "$CRITICAL_COUNT" -eq 0 && "$WARNING_COUNT" -eq 0 && "$ESCALATED" != "true" ]]; then
+  # A2 fast-path: skip remaining reviewers
+  echo "Guardian fast-path: 0 CRITICAL, 0 WARNING — skipping remaining reviewers."
+  # Proceed directly to Act phase
+fi
+```
+
+**Exception:** First cycle of `thorough` workflows always spawns all reviewers, even if Guardian is clean.
+
+### Step 3: Parallel Reviewer Spawning
+
+If A2 does not trigger, spawn remaining reviewers in parallel based on workflow:
+
+| Workflow | Reviewers (after Guardian) |
+|----------|--------------------------|
+| `fast` | None (Guardian only) |
+| `fast` (escalated via A1) | Skeptic + Sage |
+| `standard` | Skeptic + Sage |
+| `thorough` | Skeptic + Sage + Trickster |
+
+Spawn all applicable reviewers in a single message with multiple Agent calls:
+
+```
+# Standard workflow example — spawn Skeptic and Sage in parallel:
+Agent(
+  description: "Skeptic: challenge assumptions for <task>",
+  prompt: "<Skeptic prompt with Creator's proposal>",
+  model: <resolve_model skeptic $WORKFLOW>
+)
+
+Agent(
+  description: "Sage: holistic quality review for <task>",
+  prompt: "<Sage prompt with proposal + diff + implementation summary>",
+  model: <resolve_model sage $WORKFLOW>
+)
+```
+
+Each reviewer gets context per the attention filters defined in `archeflow:orchestration`:
+- **Skeptic:** Creator's proposal (assumptions section focus)
+- **Sage:** Creator's proposal + Maker's diff + implementation summary
+- **Trickster:** Maker's diff only
+
+### Step 4: Collect Results
+
+Wait for all spawned reviewers to return. For each:
+1. Save output to `.archeflow/artifacts/${RUN_ID}/check-<archetype>.md`
+2. Emit `review.verdict` event with findings
+3. Record sequence number for DAG parent tracking
+
+### Timeout Handling
+
+Each reviewer has a **5-minute timeout**. If a reviewer does not return within 5 minutes:
+1. Emit `agent.complete` with `"error": true, "reason": "timeout"`
+2. Log a WARNING — do not block the run
+3. Treat the timed-out reviewer as having delivered no findings (neither approved nor rejected)
+4. Proceed with available verdicts
+
+If Guardian times out, this is a blocking failure — abort the Check phase and report to the user.
+
+### Re-Check Protocol (Act Phase Fixes)
+
+When the Act phase routes findings back to the Maker and the Maker applies fixes in a subsequent cycle, the Check phase re-runs with the updated diff. Reviewers who previously rejected should focus on whether their specific findings were addressed. The structured feedback from `act-feedback.md` provides the mapping of which findings were routed where.
+
+---
+
 ## Why Structured Findings Matter
 
 The standardized format enables: