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/number_ops/component.contract.yaml

@@ -0,0 +1,62 @@
+canonical_id: "number_ops"
+display_name: "數字操作"
+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, input]
+  properties:
+    operation:
+      type: string
+      enum: [round, floor, ceil, abs, add, subtract, multiply, divide, mod, min, max, format]
+    input:
+      type: number
+    args:
+      type: object
+      properties:
+        value:
+          type: number
+        decimals:
+          type: number
+output_schema:
+  type: object
+  properties:
+    success:
+      type: boolean
+    data:
+      type: object
+      properties:
+        result: {}
+        operation:
+          type: string
+gherkin_tests:
+  - scenario: "round 操作"
+    given: '{"operation":"round","input":3.14}'
+    then_contains: '"result":3'
+  - scenario: "add 操作"
+    given: '{"operation":"add","input":10,"args":{"value":5}}'
+    then_contains: '"result":15'
+  - scenario: "除以零"
+    given: '{"operation":"divide","input":10,"args":{"value":0}}'
+    then_contains: '{"success":false'
+tags: [builtin, data, number, math, transform]
+description: "數字操作：round/floor/ceil/abs/add/subtract/multiply/divide/mod/min/max/format。"
+config_example: |
+  my_number_op:                           # 節點名稱（可自訂）
+    operation: "add"                      # 運算類型（必填），可選值：round/floor/ceil/abs/add/subtract/multiply/divide/mod/min/max/format
+    input: 10                             # 輸入數字（必填）
+    args:                                 # 操作參數，依 operation 而定（選填）
+      value: 5                            # add/subtract/multiply/divide/mod/min/max 用：第二個運算元
+      decimals: 2                         # round/format 用：小數位數

registry/components/number_ops/go.mod

@@ -0,0 +1,3 @@
+module component
+
+go 1.21

registry/components/number_ops/main.go

@@ -0,0 +1,100 @@
+// number_ops — 數字操作
+// 支援: round, floor, ceil, abs, add, subtract, multiply, divide, mod, min, max, format
+//
+//go:build tinygo
+
+package main
+
+import (
+	"encoding/json"
+	"io"
+	"math"
+	"os"
+	"strconv"
+)
+
+type Args struct {
+	Value    float64 `json:"value"`
+	Decimals int     `json:"decimals"`
+}
+
+type Input struct {
+	Operation string  `json:"operation"`
+	Input     float64 `json:"input"`
+	Args      Args    `json:"args"`
+}
+
+func main() {
+	raw, err := io.ReadAll(os.Stdin)
+	if err != nil {
+		writeError("failed to read stdin: " + err.Error())
+		return
+	}
+	var input Input
+	if err := json.Unmarshal(raw, &input); err != nil {
+		writeError("invalid input JSON: " + err.Error())
+		return
+	}
+	if input.Operation == "" {
+		writeError("operation 必填")
+		return
+	}
+
+	var result interface{}
+
+	switch input.Operation {
+	case "round":
+		result = math.Round(input.Input)
+	case "floor":
+		result = math.Floor(input.Input)
+	case "ceil":
+		result = math.Ceil(input.Input)
+	case "abs":
+		result = math.Abs(input.Input)
+	case "add":
+		result = input.Input + input.Args.Value
+	case "subtract":
+		result = input.Input - input.Args.Value
+	case "multiply":
+		result = input.Input * input.Args.Value
+	case "divide":
+		if input.Args.Value == 0 {
+			writeError("除數不能為 0")
+			return
+		}
+		result = input.Input / input.Args.Value
+	case "mod":
+		if input.Args.Value == 0 {
+			writeError("除數不能為 0")
+			return
+		}
+		result = math.Mod(input.Input, input.Args.Value)
+	case "min":
+		result = math.Min(input.Input, input.Args.Value)
+	case "max":
+		result = math.Max(input.Input, input.Args.Value)
+	case "format":
+		decimals := input.Args.Decimals
+		if decimals < 0 {
+			decimals = 0
+		}
+		result = strconv.FormatFloat(input.Input, 'f', decimals, 64)
+	default:
+		writeError("不支援的 operation: " + input.Operation)
+		return
+	}
+
+	out, _ := json.Marshal(map[string]interface{}{
+		"success": true,
+		"data": map[string]interface{}{
+			"result":    result,
+			"operation": input.Operation,
+		},
+	})
+	os.Stdout.Write(out)
+}
+
+func writeError(msg string) {
+	out, _ := json.Marshal(map[string]interface{}{"success": false, "error": msg})
+	os.Stdout.Write(out)
+}