docs(registry): seed 10 examples + 5 skills (LI SDD M3.1 + M3.3)

對應 .agents/specs/llm-interface/ Milestone 3.1 + 3.3。

registry/examples/ — 10 個可直接 push 的 workflow 範本：
  starter:    webhook-to-http
  common:     cron-watcher, llm-classify, rag-search-answer, daily-digest
  external:   email-summary (gmail+claude+telegram), pdf-to-blocks,
              github-issue-bot
  advanced:   parallel-fanout (trigger_workflow fan-out),
              error-retry (try_catch+wait pattern)

  每個含：workflow.yaml（可直接 push）+ description.md（解決什麼問題 /
  改成你自己的 / 學到什麼）+ tags.json（搜尋用）

registry/skills/ — 5 個 AI playbook（markdown）：
  build_watcher_workflow            — cron + filter + trigger 模式
  debug_paused_workflow             — claude_api callback paused 怎麼追
  migrate_http_to_trigger_workflow  — 從 self-fetch 換 trigger_workflow
  rag_with_arcrun                   — KBDB + claude_api 組裝 RAG
  add_new_wasm_component            — TinyGo 寫 + 部署全流程

兩者差異：
  examples = 可直接拿來改的 YAML
  skills = 面對 X 問題該怎麼想 + 該用哪個 example

兩者後續：CI 自動同步進 KBDB（type=workflow-example / type=agent-skill），
MCP arcrun_search_examples / arcrun_list_skills 走 KBDB semantic search。
（CI sync 是 M3.4 工作）

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

registry/examples/cron-watcher/workflow.yaml

@@ -0,0 +1,38 @@
+name: cron_watcher_example
+description: 每 5 分鐘掃 KBDB 未處理的 note → 對每筆觸發子 workflow
+
+flow:
+  - "watch_cron >> ON_SUCCESS >> list_unprocessed"
+  - "list_unprocessed >> ON_SUCCESS >> filter_new"
+  - "filter_new >> 對每個 item >> trigger_processor"
+
+config:
+  watch_cron:
+    component: cron
+    cron_expr: "*/5 * * * *"
+    description: "每 5 分鐘掃一次"
+
+  list_unprocessed:
+    component: kbdb_get
+    api_key: "{{api_key}}"
+    type: "note"
+    source: "user-input"
+    limit: 20
+
+  filter_new:
+    component: filter
+    items: "{{list_unprocessed.blocks}}"
+    condition:
+      key: "tags_json"
+      op: "eq"
+      value: "[]"
+
+  # trigger_workflow 是內建 orchestration 零件，in-process call 另一個 workflow
+  # **千萬不要用 http_request 自打 cypher-executor 自己的 webhook** — 會撞 CF self-fetch 死鎖
+  trigger_processor:
+    component: trigger_workflow
+    workflow_name: "your_processor_workflow"   # ← 改成你的處理 workflow 名
+    api_key: "{{api_key}}"
+    input:
+      api_key: "{{api_key}}"
+      block_id: "{{item.id}}"