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>

.component-builds/kbdb_get/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "arcrun-kbdb-get",
+  "version": "1.0.0",
+  "private": true,
+  "type": "module",
+  "dependencies": {
+    "hono": "^4.7.0"
+  },
+  "devDependencies": {
+    "@cloudflare/workers-types": "^4.20250408.0",
+    "typescript": "^5.4.0",
+    "wrangler": "^4.0.0"
+  }
+}