feat(arcrun): recipe system + resumable workflow + component registry canon

Three new platform capabilities + one component (kbdb_get) to enable
real AI workflow execution through cypher binding YAML.

## Recipe System (容器 + Recipe 模式)
SDD: .agents/specs/recipe-system/

- prompt_recipe schema (Zod): fragments + inputs + assembly + output
- recipe-expander.ts: expand recipe ref → real prompt by fetching KBDB blocks
  + pulling context fields with transforms (pluck_content / extract_field / etc)
- 7 transform whitelist: json_array / to_string / join / markdown_list /
  extract_field / first / pluck_content
- graph-executor hooks: detect node.data.recipe → expand → inject into ctx
- output JSON parser (with markdown fence stripping for Claude-wrapped JSON)
- Stored in RECIPES KV under prompt_recipe:{name}

## Resumable Workflow (webhook callback resume)
SDD: .agents/specs/resumable-workflow/

- WorkflowPaused class + paused-runs.ts (persist/load/consume in EXEC_CONTEXT KV, 24h TTL)
- graph-executor: detect {pending:true, task_id} → persist state → throw WorkflowPaused
- cypher-handlers: catch → return {success:true, paused:true, task_id, run_id}
- POST /workflows/resume route: consume KV state → resumeFromPaused()
- Auto-inject callback_url for claude_api nodes (PUBLIC_BASE_URL or default cypher.arcrun.dev)
- claude_api/main.go: forward callback_url to Mira daemon, default timeout 25s→120s
- Idempotent (consume = load+delete)

## Component Registry Canon
SDD: .agents/specs/component-registry-canon/

- Add POST /components/index-only endpoint (metadata-only, no wasm/sandbox)
- Backfill script (mjs): scan registry/components/*/contract.yaml → submit to KV
- register-component.sh: SSOT for local + CI hook (deploy.yml change in next commit)
- Drop R2 dead storage from submitComponent + types + wrangler
- Schema relaxed: category enum + auth/ai/platform; cold_start 50→500ms; size 2→8MB

## kbdb_get component
- registry/components/kbdb_get/: TinyGo WASM, two modes (block_id / page_name list)
- .component-builds/kbdb_get/: WASI shim worker (kbdb-get.arcrun.dev)

End-to-end validation: AI uses MCP execute_workflow with recipe ref →
cypher-executor expands prompt from KBDB schema/skill blocks + drafts →
claude_api calls Mira daemon → daemon callback fires resume route →
workflow continues. Verified with real 2KB+ Karpathy LLM Wiki draft.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

registry/components/kbdb_get/component.contract.yaml

@@ -0,0 +1,69 @@
+canonical_id: "kbdb_get"
+display_name: "KBDB 讀取"
+category: "data"
+version: "v1"
+wasi_target: "preview1"
+stability: "floating"
+runtime_compat:
+  - "cf-workers"
+  - "workerd"
+  - "wazero"
+constraints:
+  max_size_kb: 2048
+  max_cold_start_ms: 50
+  no_network_syscall: false
+  no_filesystem_syscall: true
+  io_model: "stdin_stdout_json"
+input_schema:
+  type: object
+  required: [api_key]
+  properties:
+    api_key:
+      type: string
+      description: KBDB partner key（pk_live_xxx 或 ak_xxx）
+    block_id:
+      type: string
+      description: 取單一 block。給 block_id 走 GET /blocks/{id}，與 page_name 二擇一
+    page_name:
+      type: string
+      description: 按 page_name 查列表。走 GET /blocks?page_name=...&limit=N
+    limit:
+      type: integer
+      description: page_name 模式下的最大筆數，預設 50
+      default: 50
+    kbdb_url:
+      type: string
+      description: KBDB API base（選填，預設 https://kbdb.finally.click）
+      default: "https://kbdb.finally.click"
+output_schema:
+  type: object
+  properties:
+    success:
+      type: boolean
+    blocks:
+      type: array
+      description: page_name 模式回多個 block；block_id 模式回 1 個（仍包成陣列方便下游 foreach）
+      items:
+        type: object
+    count:
+      type: integer
+      description: blocks.length
+    error:
+      type: string
+gherkin_tests:
+  - scenario: "缺 api_key"
+    given: '{"page_name":"x"}'
+    then_contains: '{"success":false'
+  - scenario: "block_id 與 page_name 都沒給"
+    given: '{"api_key":"pk_live_x"}'
+    then_contains: '{"success":false'
+tags: [data, storage, kbdb, get, query, primitive]
+description: "從 KBDB 讀 block。支援兩種模式：(1) block_id 取單一 block；(2) page_name 取列表。透過 host function http_request 呼叫 KBDB GET /blocks 或 /blocks/:id。Mira wiki 合成 / 各 source workflow 讀草稿 / 查 wiki schema 都走這條。"
+config_example: |
+  read_schema:                # 取單一 block
+    api_key: "{{secret.kbdb_key}}"
+    page_name: "mira-wiki-schema"
+  read_drafts:                # 取列表
+    api_key: "{{secret.kbdb_key}}"
+    page_name: "{{prev.entity_name}}"
+    limit: 100