initial: canary multi-agent skills with tmux isolation support

- lib.sh: TMUX_SERVER_NAME env var, _tmux helper, shim externalized
  to TMPDIR with recursive guard, resolve_tmux_server helper for
  YAML-driven server routing
- multi-agent-create: --tmux-server opt-in flag, YAML tmux_server
  field for orphan prevention
- multi-agent-delete/resume/status/agent-sessions-monitor: use
  resolve_tmux_server to auto-route to correct isolated server
- SKILL.md × 4: documented isolation server workflow
- Verified by claude review (R1+re-run) + agy R2 patches
  (orphan prevention + shim location fix)

.gitignore

@@ -0,0 +1,11 @@
+# 1회성 작업 자료 (agy/claude 워커에게 보낸 프롬프트)
+_agy_prompt_*.md
+_claude_prompt_*.md
+
+# 임시 검증용 산출물
+test-sessions.yaml
+test-sessions.yaml.bak
+test-sessions.yaml.lock
+
+# 자체 git repo 임베드 (별도 관리)
+delegate-job-skill/