arcrun — AI workflow execution engine (clean history)

Self-hosted 開源：WASM 零件 + recipe + cypher-executor，跑在你自己的 Cloudflare。

此為重建的乾淨歷史起點（移除曾誤 commit 的 GCP SA 金鑰，舊歷史保留在
richblack/arcrun 與本地 backup 分支）。含：
- acr init --self-hosted installer（建 KV/R2 + codeload 拉預編譯 wasm + wrangler deploy + seed recipe）
- recipe push 把關（資料外流提醒 + 打通檢查）
- 19 個正當零件預編譯 wasm（claude_api/km_writer/kbdb_upsert_block 排除：違反 DECISIONS §1）
- CLI / cypher-executor / registry / 完整 SDD

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.component-builds/km_writer/src/index.ts

@@ -0,0 +1,77 @@
+/**
+ * arcrun API component Worker (km_writer)
+ *
+ * POST / → JSON input → WASM (WASI preview1 stdin/stdout) → JSON output
+ *
+ * 提供 http_request host function，讓 WASM 零件呼叫 Mira /km/* API。
+ */
+
+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: 'km_writer' }));
+
+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;
+
+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();
+  if (!stdout) throw new Error('WASM component produced no output');
+  return JSON.parse(stdout);
+}