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>

registry/components/cron/component.contract.yaml

@@ -0,0 +1,57 @@
+canonical_id: "cron"
+display_name: "定時排程"
+category: "logic"
+version: "v1"
+wasi_target: "preview1"
+stability: "floating"
+runtime_compat:
+  - "cf-workers"
+  - "workerd"
+  - "wazero"
+constraints:
+  max_size_kb: 2048
+  max_cold_start_ms: 50
+  no_network_syscall: true
+  no_filesystem_syscall: true
+  io_model: "stdin_stdout_json"
+input_schema:
+  type: object
+  required: [cron_expr]
+  properties:
+    cron_expr:
+      type: string
+      description: 標準 5 欄位 cron expression，如 0 9 * * *
+    description:
+      type: string
+output_schema:
+  type: object
+  properties:
+    success:
+      type: boolean
+    data:
+      type: object
+      properties:
+        cron_id:
+          type: string
+        cron_expr:
+          type: string
+        enabled:
+          type: boolean
+        description:
+          type: string
+gherkin_tests:
+  - scenario: "有效 cron expression"
+    given: '{"cron_expr":"0 9 * * *","description":"每天早上9點"}'
+    then_contains: '"enabled":true'
+  - scenario: "無效 cron expression（欄位數不對）"
+    given: '{"cron_expr":"0 9 * *"}'
+    then_contains: '{"success":false'
+  - scenario: "缺少 cron_expr"
+    given: '{}'
+    then_contains: '{"success":false'
+tags: [builtin, cron, schedule, trigger, timer]
+description: "驗證 cron expression 格式並回傳 cron_id。實際排程由 Cypher Executor 負責。"
+config_example: |
+  my_cron:                                # 節點名稱（可自訂）
+    cron_expr: "0 9 * * *"               # 標準 5 欄位 cron 表達式（必填），如：每天早上 9 點
+    description: "每天早上9點執行"        # 排程說明文字（選填）