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/http_request/component.contract.yaml

@@ -0,0 +1,62 @@
+canonical_id: "http_request"
+display_name: "HTTP 請求"
+category: "api"
+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: [url]
+  properties:
+    url:
+      type: string
+      description: 目標 URL（必填）
+    method:
+      type: string
+      description: HTTP 方法（GET / POST / PUT / DELETE 等），預設 GET
+      default: GET
+    headers:
+      type: object
+      description: 自訂 HTTP headers（key-value 物件）
+      additionalProperties:
+        type: string
+    body:
+      description: 請求 body（任意 JSON）
+output_schema:
+  type: object
+  properties:
+    success:
+      type: boolean
+    data:
+      type: object
+      properties:
+        body:
+          type: string
+          description: HTTP 回應 body（字串）
+gherkin_tests:
+  - scenario: "缺少 url"
+    given: '{"method":"GET"}'
+    then_contains: '{"success":false'
+  - scenario: "基本 GET 請求"
+    given: '{"url":"https://example.com"}'
+    then_contains: '{"success":true'
+tags: [integration, http, request, api]
+description: "發送任意 HTTP 請求並回傳 status 與 body。透過 host function 呼叫，.wasm 本身不含網路 syscall。headers 由用戶手動填入。"
+config_example: |
+  http_call:                     # 節點名稱（可自訂）
+    url: ""                      # 目標 URL（必填）
+    method: "GET"                # HTTP 方法（選填，預設 GET）
+    headers:                     # 自訂 headers（選填，用戶手動填入）
+      Content-Type: "application/json"
+      Authorization: "Bearer <your_token>"
+    body: {}                     # 請求 body（選填）