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/src/index.ts

@@ -0,0 +1,82 @@
+/**
+ * arcrun WASM 零件 Worker (kbdb_get)
+ *
+ * POST / → JSON input → WASM (WASI preview1 stdin/stdout) → JSON output
+ *
+ * host function: http_request（用於呼叫 KBDB API）
+ * SDD: polaris/mira/.agents/specs/mira-app/design.md §6 / tasks.md §5.3
+ */
+
+import componentWasm from '../component.wasm' assert { type: 'webassembly' };
+import { Hono } from 'hono';
+import { cors } from 'hono/cors';
+import { createWasiShim, type WasiHostFunctions } from '../../../cypher-executor/src/lib/wasi-shim';
+
+const app = new Hono();
+app.use('*', cors());
+
+app.get('/', (c) => c.json({ ok: true, component: 'kbdb_get' }));
+
+app.post('/', async (c) => {
+  let input: unknown;
+  try {
+    input = await c.req.json();
+  } catch {
+    return c.json({ success: false, error: 'request body must be JSON' }, 400);
+  }
+
+  try {
+    const result = await runWasm(input);
+    return c.json(result);
+  } catch (e) {
+    return c.json(
+      { success: false, error: e instanceof Error ? e.message : String(e) },
+      500,
+    );
+  }
+});
+
+export default app;
+
+// ── WASM runner ──────────────────────────────────────────────────────────────
+
+async function runWasm(input: unknown): Promise<unknown> {
+  const hostFunctions: WasiHostFunctions = {
+    http_request: async (url, method, headersJson, body) => {
+      const headers: Record<string, string> = {};
+      if (headersJson) {
+        try {
+          const parsed = JSON.parse(headersJson);
+          if (parsed && typeof parsed === 'object') {
+            for (const [k, v] of Object.entries(parsed as Record<string, unknown>)) {
+              if (typeof v === 'string') headers[k] = v;
+            }
+          }
+        } catch {
+          // ignore header parse errors
+        }
+      }
+      const init: RequestInit = { method, headers };
+      if (body && method.toUpperCase() !== 'GET' && method.toUpperCase() !== 'HEAD') {
+        init.body = body;
+      }
+      const res = await fetch(url, init);
+      return await res.text();
+    },
+  };
+
+  const shim = createWasiShim(JSON.stringify(input), hostFunctions);
+
+  const instance = await WebAssembly.instantiate(
+    componentWasm as WebAssembly.Module,
+    shim.imports,
+  );
+  shim.setMemory(instance.exports.memory as WebAssembly.Memory);
+  await shim.run(instance);
+
+  const stdout = shim.getStdout().trim();
+  const stderr = shim.getStderr().trim();
+  if (stderr) console.error('[kbdb_get wasm stderr]', stderr);
+  if (!stdout) throw new Error('WASM component produced no output');
+  return JSON.parse(stdout);
+}