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/if_control/main.go

@@ -0,0 +1,138 @@
+// if_control — 單一條件判斷，true/false 兩個出口
+// condition 支援：key（truthy）、key == value、key > number、key < number
+package main
+
+import (
+	"encoding/json"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+)
+
+type Input struct {
+	Condition string                 `json:"condition"`
+	Input     map[string]interface{} `json:"input"`
+}
+
+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.Condition == "" {
+		writeError("condition 必填")
+		return
+	}
+
+	result := evaluateCondition(input.Condition, input.Input)
+	branch := "false"
+	if result {
+		branch = "true"
+	}
+
+	out, _ := json.Marshal(map[string]interface{}{
+		"success": true,
+		"data":    map[string]interface{}{"result": result, "branch": branch},
+	})
+	os.Stdout.Write(out)
+}
+
+func toString(v interface{}) string {
+	switch val := v.(type) {
+	case string:
+		return val
+	case float64:
+		return strconv.FormatFloat(val, 'f', -1, 64)
+	case bool:
+		if val {
+			return "true"
+		}
+		return "false"
+	case nil:
+		return ""
+	default:
+		b, _ := json.Marshal(val)
+		return string(b)
+	}
+}
+
+func evaluateCondition(condition string, ctx map[string]interface{}) bool {
+	if ctx == nil {
+		return false
+	}
+	expr := strings.TrimSpace(condition)
+
+	// key == value
+	if idx := strings.Index(expr, "=="); idx > 0 {
+		key := strings.TrimSpace(expr[:idx])
+		expected := strings.Trim(strings.TrimSpace(expr[idx+2:]), `"'`)
+		v, ok := ctx[key]
+		if !ok {
+			return false
+		}
+		return toString(v) == expected
+	}
+	// key > number
+	if idx := strings.Index(expr, ">"); idx > 0 {
+		key := strings.TrimSpace(expr[:idx])
+		threshold, err := strconv.ParseFloat(strings.TrimSpace(expr[idx+1:]), 64)
+		if err != nil {
+			return false
+		}
+		v, ok := ctx[key]
+		if !ok {
+			return false
+		}
+		n, err := strconv.ParseFloat(toString(v), 64)
+		if err != nil {
+			return false
+		}
+		return n > threshold
+	}
+	// key < number
+	if idx := strings.Index(expr, "<"); idx > 0 {
+		key := strings.TrimSpace(expr[:idx])
+		threshold, err := strconv.ParseFloat(strings.TrimSpace(expr[idx+1:]), 64)
+		if err != nil {
+			return false
+		}
+		v, ok := ctx[key]
+		if !ok {
+			return false
+		}
+		n, err := strconv.ParseFloat(toString(v), 64)
+		if err != nil {
+			return false
+		}
+		return n < threshold
+	}
+	// truthy check
+	v, ok := ctx[expr]
+	if !ok {
+		return false
+	}
+	switch val := v.(type) {
+	case bool:
+		return val
+	case string:
+		return val != ""
+	case float64:
+		return val != 0
+	case nil:
+		return false
+	default:
+		return true
+	}
+}
+
+func writeError(msg string) {
+	out, _ := json.Marshal(map[string]interface{}{"success": false, "error": msg})
+	os.Stdout.Write(out)
+}