fix(arcrun): address PR #2 review findings

Security:
- init.ts: remove cf_api_token from POST /register (only email sent to arcrun.dev)
- cf-api.ts: remove base64 fallback in encryptCredential, throw clear error if key missing

Correctness:
- submitComponent.ts: replace KBDB dependency with SUBMISSIONS_KV + R2 (standalone)
- registry/types.ts: remove KBDB_URL/KBDB_INTERNAL_TOKEN, add SUBMISSIONS_KV/ANALYTICS_KV
- webhooks.ts: add waitUntil(writeExecutionVerdict) for fire-and-forget analytics
- execution-logger.ts: create missing module (was imported but didn't exist)
- cypher-executor/types.ts + wrangler.toml: add ANALYTICS_KV binding
- gmail/telegram/google_sheets/line_notify/http_request: no_network_syscall false (api category)
- init.ts: replace require() with await import() for ES module compatibility

Cleanup:
- Remove arcrun/builtins/ (dead code — initComponents used old HTTP endpoint model,
  all 21 components now in TinyGo WASM under registry/components/)

Docs:
- tasks.md: update to reflect completed work and remaining items

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cypher-executor/src/actions/execution-logger.ts

@@ -0,0 +1,53 @@
+/**
+ * Execution Logger — 執行結果寫入 ANALYTICS_KV（fire-and-forget）
+ *
+ * 設計：每次 workflow 執行後，將統計數據寫入 ANALYTICS_KV（key = stats:{workflowId}）。
+ * Phase 7 可升級為 POST 至 registry.arcrun.dev/analytics/record。
+ */
+
+import type { Bindings, GraphNode } from '../types';
+
+export interface ExecutionVerdict {
+  workflow_id: string;
+  component_ids: string[];
+  verdict: 'success' | 'failed';
+  duration_ms: number;
+  message: string;
+  recorded_at: string;
+}
+
+/**
+ * 寫入執行結果至 ANALYTICS_KV（fire-and-forget，不阻擋主流程）
+ * 由 c.executionCtx.waitUntil() 包裹呼叫
+ */
+export async function writeExecutionVerdict(
+  env: Bindings,
+  workflowId: string,
+  nodes: GraphNode[],
+  verdict: 'success' | 'failed',
+  durationMs: number,
+  message: string,
+): Promise<void> {
+  try {
+    const componentIds = nodes
+      .filter(n => n.type === 'Component' && n.componentId)
+      .map(n => n.componentId!);
+
+    const record: ExecutionVerdict = {
+      workflow_id: workflowId,
+      component_ids: componentIds,
+      verdict,
+      duration_ms: durationMs,
+      message,
+      recorded_at: new Date().toISOString(),
+    };
+
+    // ANALYTICS_KV key = stats:{workflowId}:{timestamp}（避免覆蓋）
+    const key = `stats:${workflowId}:${Date.now()}`;
+    await env.ANALYTICS_KV.put(key, JSON.stringify(record), {
+      expirationTtl: 60 * 60 * 24 * 90, // 保留 90 天
+    });
+  } catch {
+    // fire-and-forget：不拋錯，不影響主流程
+  }
+}