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

registry/components/date_ops/component.contract.yaml

@@ -0,0 +1,61 @@
+canonical_id: "date_ops"
+display_name: "日期操作"
+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: [operation]
+  properties:
+    operation:
+      type: string
+      enum: [now, format, parse]
+    input:
+      type: string
+      description: ISO 日期字串（now 操作可省略）
+    args:
+      type: object
+      properties:
+        layout:
+          type: string
+          description: Go time layout（如 2006-01-02）
+output_schema:
+  type: object
+  properties:
+    success:
+      type: boolean
+    data:
+      type: object
+      properties:
+        result: {}
+        operation:
+          type: string
+gherkin_tests:
+  - scenario: "now 操作"
+    given: '{"operation":"now"}'
+    then_contains: '"success":true'
+  - scenario: "parse 操作"
+    given: '{"operation":"parse","input":"2024-01-15T10:30:00Z"}'
+    then_contains: '"year":2024'
+  - scenario: "無效日期"
+    given: '{"operation":"parse","input":"not-a-date"}'
+    then_contains: '{"success":false'
+tags: [builtin, data, date, time, transform]
+description: "日期操作：now（當前時間）、format（格式化）、parse（解析 ISO 字串）。"
+config_example: |
+  my_date_op:                             # 節點名稱（可自訂）
+    operation: "format"                   # 運算類型（必填），可選值：now/format/parse
+    input: "2024-01-15T10:30:00Z"        # ISO 日期字串（now 操作可省略，其餘必填）
+    args:                                 # 操作參數（選填）
+      layout: "2006-01-02"               # format 用：Go time layout 格式字串