Deliver API keys through exclusive private files

Why: API-key issuance shares the account maintenance no-create and credential-output contract; the old CLI printed its key and lacked --out-file.

Evidence: The new subprocess test failed before the flag existed, then passed for private output and pre-mutation collision refusal; current go vet and all Go tests pass.

Impact: apikey create accepts protected --dsn-file and --out-file, preserves stdout default, and never overwrites an existing destination.

Refs: Backend PR #185; Dev PR #486; U7 KTD14

cmd/agent-system/account_io_test.go

@@ -2,8 +2,10 @@ package main
 
 import (
 	"agent-system-backend/internal/store"
+	"bytes"
 	"io"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"testing"
 )
@@ -88,3 +90,69 @@ func TestExistingOutputAndConflictingFormatsRefuseBeforeMutation(t *testing.T) {
 		})
 	}
 }
+
+func TestAPIKeyCreateUsesExclusivePrivateOutput(t *testing.T) {
+	if dir := os.Getenv("U7_APIKEY_CHILD_DIR"); dir != "" {
+		rc := runAPIKey([]string{"create", "--data", dir, "--owner", "ada", "--name", "fixture", "--out-file", os.Getenv("U7_APIKEY_CHILD_OUT")})
+		if rc != 0 {
+			t.Fatal("apikey create rejected its private output destination")
+		}
+		return
+	}
+	for _, existing := range []bool{false, true} {
+		name := "new"
+		if existing {
+			name = "existing"
+		}
+		t.Run(name, func(t *testing.T) {
+			dir, st := cliStore(t)
+			if err := st.CreateAccount("ada", "Ada", "", false); err != nil {
+				t.Fatal(err)
+			}
+			out := filepath.Join(t.TempDir(), "credential")
+			if existing {
+				if err := os.WriteFile(out, []byte("preserve"), 0600); err != nil {
+					t.Fatal(err)
+				}
+			}
+			cmd := exec.Command(os.Args[0], "-test.run=^TestAPIKeyCreateUsesExclusivePrivateOutput$")
+			cmd.Env = append(os.Environ(), "U7_APIKEY_CHILD_DIR="+dir, "U7_APIKEY_CHILD_OUT="+out)
+			var stdout, stderr bytes.Buffer
+			cmd.Stdout = &stdout
+			cmd.Stderr = &stderr
+			err := cmd.Run()
+			if existing {
+				if err == nil {
+					t.Fatal("existing output was overwritten or mutation succeeded")
+				}
+				raw, readErr := os.ReadFile(out)
+				if readErr != nil || string(raw) != "preserve" {
+					t.Fatal("existing output was modified")
+				}
+				keys, listErr := st.ListAPIKeys("ada")
+				if listErr != nil || len(keys) != 0 {
+					t.Fatal("mutation happened before output preflight")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatal("new private output was rejected")
+			}
+			info, statErr := os.Stat(out)
+			if statErr != nil || info.Mode().Perm() != 0600 {
+				t.Fatal("credential output missing or not private")
+			}
+			raw, readErr := os.ReadFile(out)
+			if readErr != nil || len(raw) == 0 {
+				t.Fatal("credential output empty")
+			}
+			if bytes.Contains(stdout.Bytes(), bytes.TrimSpace(raw)) {
+				t.Fatal("credential was written to stdout")
+			}
+			keys, listErr := st.ListAPIKeys("ada")
+			if listErr != nil || len(keys) != 1 {
+				t.Fatal("successful issue was not committed")
+			}
+		})
+	}
+}

cmd/agent-system/main.go

@@ -196,22 +196,43 @@ func runAPIKey(args []string) int {
 	fs := flag.NewFlagSet("apikey "+sub, flag.ExitOnError)
 	data := fs.String("data", "./data", "数据目录")
 	dsn := fs.String("dsn", "", "PostgreSQL 档 DSN（空 = 嵌入式档）")
+	dsnFile := fs.String("dsn-file", "", "0600权限的PostgreSQL DSN文件")
 	owner := fs.String("owner", "", "租户名（owner）")
 	name := fs.String("name", "default", "密钥名称")
+	outFile := fs.String("out-file", "", "把明文密钥独占写入该文件（0600）")
 	fs.Parse(args[1:])
 	if *owner == "" {
 		fmt.Fprintln(os.Stderr, "apikey: --owner 必填")
 		return 2
 	}
+	if sub != "create" && *outFile != "" {
+		fmt.Fprintln(os.Stderr, "apikey: 此子命令不生成密钥")
+		return 2
+	}
+	resolvedDSN, err := resolveAccountDSN(*dsn, *dsnFile)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "apikey:", err)
+		return 1
+	}
+	*dsn = resolvedDSN
 	switch sub {
 	case "create":
+		delivery, err := reserveCredentialOutput(*outFile, "")
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "apikey create:", err)
+			return 1
+		}
+		defer delivery.abort()
 		key, err := app.CreateAPIKey(*dsn, *data, *owner, *name)
 		if err != nil {
 			fmt.Fprintln(os.Stderr, "apikey create:", err)
 			return 1
 		}
 		// 明文仅此一次输出；库中只存 SHA-256 摘要。
-		fmt.Println(key)
+		if err := delivery.deliver("api-key", *owner, key, nil); err != nil {
+			fmt.Fprintln(os.Stderr, "apikey create:", err)
+			return 1
+		}
 		return 0
 	case "list":
 		keys, err := app.ListAPIKeys(*dsn, *data, *owner)