docs(delegate-job): add Subagent Orchestration Pattern section to SKILL.md

Verified pattern from 2026-06-21 6-batch refactoring sprint:
- Main worker (agy-new) + 2 reviewers (agy-existing, claude-existing) + Hermes orchestrator
- Brief delivery via file path (not inline tmux send-keys)
- Polling for short tasks, MQTT subscriber for long tasks
- Complementary reviewer coverage (different models catch different bugs)
- Hermes fallback fix for small well-defined issues
- Batch grouping rules (no file overlap)

skills/tmux-agent-orchestrate-delegate-job/SKILL.md

@@ -317,6 +317,39 @@ business-logic validation — those are hooks you fill (`validate.sh` reads
 - **Secrets in `detail`/`data`** — keep payloads generalised; no paths, keys, or
   tokens (except the production `auth_token` in `data`).
 
+## Subagent Orchestration Pattern
+
+When using this skill from a Hermes `delegate_task` subagent to dispatch work to
+a coding-agent CLI (agy/claude) running in a tmux session, the following pattern
+has been verified (2026-06-21, 6-batch refactoring sprint):
+
+### Roles
+- **Main worker** (implementation): one agent session (e.g. `agy-new`) receives
+  brief files and executes code changes.
+- **Reviewers** (spec compliance + code quality): two other agent sessions
+  (e.g. `agy-existing`, `claude-existing`) review the diff in parallel.
+- **Hermes** (orchestrator): dispatches subagents, verifies diffs, commits,
+  and falls back to direct fixes when reviewers find issues.
+
+### Key lessons learned
+1. **Brief delivery via file path** — don't paste long briefs inline via
+   `tmux send-keys`; the TUI may swallow them. Instead, send a short instruction
+   like "follow /tmp/batch1-brief.md" and let the agent read the file.
+2. **Polling vs MQTT subscriber** — for short tasks (<5min), pane polling
+   (`capture-pane` + grep for completion markers) is simpler and more reliable
+   than registering a job via `registry.py` + `job_subscriber.py`. Use MQTT
+   subscriber only for long-running jobs (>5min) where push notification matters.
+3. **Reviewers catch different bugs** — in practice, agy (Flash) caught
+   semantic issues (slash matching, export scope), while claude (Opus) caught
+   API signature mismatches (paho v2 5-arg vs 4-arg `on_disconnect`). Two
+   reviewers with different models provide complementary coverage.
+4. **Hermes fallback fix** — when reviewers find a small, well-defined issue
+   (wrong argument count, missing slash), Hermes should fix it directly rather
+   than re-dispatching the implementer. This saves a full round-trip.
+5. **Batch grouping** — group 2-3 FW items per batch when they touch different
+   files (no file overlap). This amortises the dispatch overhead. Items touching
+   the same file must be in separate batches to avoid conflicts.
+
 ## Verification Checklist
 
 - [ ] `started` → `completed` over the public broker: subscriber prints the