add delegation mode fallback to matrix rail in kickstart

skills/kickstart/SKILL.md

@@ -84,12 +84,27 @@ Target:       [milestone/issue/task]
 Project:      [org/repo]
 Platform:     [Gitea/GitHub]
 Branch base:  [develop/main]
+Delegation:   [native-subagent | matrix-rail-fallback]
 Quality gates: [detected commands or "none detected — will ask"]
 Existing state: [docs/tasks.md found / none]
 ```
 
 Ask the user to confirm or override any detected values.
 
+### 1e. Detect delegation mode
+
+Before orchestration begins, decide delegation mode:
+
+- **native-subagent**: runtime has reliable subagent/background task primitive
+- **matrix-rail-fallback**: use deterministic Mosaic rail when native primitive is absent/unreliable
+
+Fallback commands:
+
+```bash
+~/.mosaic/bin/mosaic-orchestrator-matrix-cycle
+~/.mosaic/bin/mosaic-orchestrator-run --poll-sec 10
+```
+
 ---
 
 ## Step 2: Fetch Target Data
@@ -209,7 +224,7 @@ You are now the **orchestrator**. Follow the protocol from `~/.mosaic/guides/orc
 4. **Completed issues are closed** in the repo via `"${MOSAIC_HOME:-$HOME/.mosaic}/rails/git/issue-close.sh"`
 5. **tasks.md is the single source of truth** — you are the sole writer
 6. **Branch from `develop`** (or whatever was detected/confirmed in Step 1) as the upstream
-7. **Max 2 parallel workers** at any time
+7. **Max 2 active worker tasks** at any time (applies to native and matrix modes)
 8. **Two-Phase Completion:** Bulk phase (target 90%), then Polish phase (target 100%)
 9. **Context threshold (55-60%):** Output handoff kickstart and STOP — do not compact
 
@@ -219,11 +234,13 @@ You are now the **orchestrator**. Follow the protocol from `~/.mosaic/guides/orc
 WHILE tasks remain not-started or in-progress:
   1. Find next unblocked task (all depends_on are done)
   2. Update tasks.md: status=in-progress, started_at=now
-  3. Spawn worker via Task tool with:
+  3. Delegate worker task with:
      - Task details and acceptance criteria
      - Branch to work on
      - Quality gate commands
      - Expected JSON result format
+     - Native mode: runtime Task/subagent primitive
+     - Matrix mode: queue task in `.mosaic/orchestrator/tasks.json` and run `~/.mosaic/bin/mosaic-orchestrator-matrix-cycle`
   4. Parse worker result JSON
   5. Calculate variance: (actual - estimate) / estimate × 100
   6. Update tasks.md: status=done/failed, completed_at, used