feat(arcrun): implement arcrun MVP — open-source AI workflow engine

Phase 1-5 complete per .agents/specs/u6u-core-mvp/:

**Phase 1 — Cherry-pick & cleanup**
- Create arcrun/ from cypher-executor, credentials, builtins, registry
- Remove 9 InkStone Service Bindings (KBDB, REGISTRY, CLINIC_*, AICEO, MINI_ME)
- Rewrite component-loader: 3-layer (builtin → WASM_BUCKET R2 → error)
- Remove autoPublishMissing.ts, proxy.ts (AICEO), execution-logger.ts (KBDB)
- Clean all KV namespace IDs and InkStone internal URLs from config files

**Phase 2 — contract.yaml completeness**
- Add credentials_required to gmail, google_sheets, telegram, line_notify
- Add config_example to all 21 components with annotated field descriptions

**Phase 3 — Credential injection**
- Add credential-injector.ts: AES-GCM decrypt from CREDENTIALS_KV
- Integrate into GraphExecutor before WASM execution
- Structured errors with repair instructions when credential missing

**Phase 4 — CLI (acr)**
- cli/package.json: arcrun package, bin: acr, deps: commander/js-yaml/chalk/ora
- 8 commands: init, creds push, push, run, validate, parts, list, logs
- Standard mode: writes directly to user's CF KV via CF REST API
- acr init: interactive setup with arcrun.dev API Key registration

**Phase 5 — Open source release prep**
- README.md: 5-minute quickstart, component table, workflow YAML syntax
- CONTRIBUTING.md: TinyGo dev env, component scaffolding, submission flow
- Security audit: no InkStone internal URLs/IDs in committed files
- .gitignore: exclude credentials.yaml, .wrangler, *.wasm

https://claude.ai/code/session_01BnCdSLVH8tUed9VrrPavgT

cli/src/lib/cf-api.ts

@@ -0,0 +1,115 @@
+/**
+ * Cloudflare KV REST API wrapper
+ * 使用 CF REST API 直接存取用戶的 KV namespace，不依賴 Wrangler CLI
+ */
+
+const CF_API_BASE = 'https://api.cloudflare.com/client/v4';
+
+export interface CfKvClientOptions {
+  accountId: string;
+  namespaceId: string;
+  apiToken: string;
+}
+
+export class CfKvClient {
+  private base: string;
+  private headers: Record<string, string>;
+
+  constructor({ accountId, namespaceId, apiToken }: CfKvClientOptions) {
+    this.base = `${CF_API_BASE}/accounts/${accountId}/storage/kv/namespaces/${namespaceId}`;
+    this.headers = {
+      'Authorization': `Bearer ${apiToken}`,
+      'Content-Type': 'application/json',
+    };
+  }
+
+  async put(key: string, value: string): Promise<void> {
+    const res = await fetch(`${this.base}/values/${encodeURIComponent(key)}`, {
+      method: 'PUT',
+      headers: { ...this.headers, 'Content-Type': 'text/plain' },
+      body: value,
+    });
+    if (!res.ok) {
+      const err = await res.text();
+      throw new Error(`KV PUT 失敗（${res.status}）：${err.slice(0, 200)}`);
+    }
+  }
+
+  async get(key: string): Promise<string | null> {
+    const res = await fetch(`${this.base}/values/${encodeURIComponent(key)}`, {
+      headers: this.headers,
+    });
+    if (res.status === 404) return null;
+    if (!res.ok) {
+      const err = await res.text();
+      throw new Error(`KV GET 失敗（${res.status}）：${err.slice(0, 200)}`);
+    }
+    return res.text();
+  }
+
+  async list(prefix?: string): Promise<Array<{ name: string; expiration?: number; metadata?: unknown }>> {
+    const url = new URL(`${this.base}/keys`);
+    if (prefix) url.searchParams.set('prefix', prefix);
+    url.searchParams.set('limit', '1000');
+
+    const res = await fetch(url.toString(), { headers: this.headers });
+    if (!res.ok) {
+      const err = await res.text();
+      throw new Error(`KV LIST 失敗（${res.status}）：${err.slice(0, 200)}`);
+    }
+    const data = await res.json() as {
+      result: Array<{ name: string; expiration?: number; metadata?: unknown }>;
+    };
+    return data.result ?? [];
+  }
+
+  async delete(key: string): Promise<void> {
+    const res = await fetch(`${this.base}/values/${encodeURIComponent(key)}`, {
+      method: 'DELETE',
+      headers: this.headers,
+    });
+    if (!res.ok) {
+      const err = await res.text();
+      throw new Error(`KV DELETE 失敗（${res.status}）：${err.slice(0, 200)}`);
+    }
+  }
+}
+
+/** AES-GCM 加密 credential（與 cypher-executor credential-injector 解密邏輯對應）*/
+export async function encryptCredential(value: string, encryptionKey: string): Promise<string> {
+  // 若沒有設定 encryption key，使用 base64 作為 fallback（dev 模式）
+  if (!encryptionKey || encryptionKey.length < 32) {
+    const b64 = Buffer.from(value).toString('base64');
+    return JSON.stringify({ encrypted: b64, iv: 'dev-mode', mode: 'base64' });
+  }
+
+  const keyBytes = hexToUint8Array(encryptionKey);
+  const cryptoKey = await crypto.subtle.importKey(
+    'raw',
+    keyBytes,
+    { name: 'AES-GCM' },
+    false,
+    ['encrypt'],
+  );
+
+  const iv = crypto.getRandomValues(new Uint8Array(12));
+  const encoded = new TextEncoder().encode(value);
+  const cipherBuffer = await crypto.subtle.encrypt({ name: 'AES-GCM', iv }, cryptoKey, encoded);
+
+  return JSON.stringify({
+    encrypted: uint8ArrayToBase64(new Uint8Array(cipherBuffer)),
+    iv: uint8ArrayToBase64(iv),
+  });
+}
+
+function hexToUint8Array(hex: string): Uint8Array {
+  const bytes = new Uint8Array(hex.length / 2);
+  for (let i = 0; i < hex.length; i += 2) {
+    bytes[i / 2] = parseInt(hex.slice(i, i + 2), 16);
+  }
+  return bytes;
+}
+
+function uint8ArrayToBase64(arr: Uint8Array): string {
+  return Buffer.from(arr).toString('base64');
+}