feat(cli): agent-readable account list (reduced JSON view)

account list now routes to the agent role; an agent (EMCLI_KEY only) gets a
JSON envelope of name/from/can_send, while the admin keeps the full text
table. account add/edit/remove stay admin-only.

Also emit the agent path's missing-key/open failure as a JSON Failure
envelope (per spec), and update the stale run_test case that asserted the
old admin-only behavior.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/cli/admin.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"strconv"
 
+	"git.dcglab.co.uk/steve/emcli/internal/crypto"
 	"git.dcglab.co.uk/steve/emcli/internal/store"
 	"git.dcglab.co.uk/steve/emcli/internal/tui"
 )
@@ -23,7 +24,14 @@ func runAccount(args []string, role store.Role, out, errOut io.Writer) int {
 	sub, rest := args[0], args[1:]
 	st, err := openStore(role)
 	if err != nil {
-		fmt.Fprintf(errOut, "emcli: %v\n", err)
+		// account list is an agent command (a JSON consumer), so its
+		// open/key failures are emitted as an envelope, like the other agent
+		// commands; the admin subcommands stay human-readable.
+		if sub == "list" {
+			_ = Failure(CodeConfig, err.Error()).Write(out)
+		} else {
+			fmt.Fprintf(errOut, "emcli: %v\n", err)
+		}
 		return 1
 	}
 	defer st.Close()
@@ -171,11 +179,31 @@ func runAccount(args []string, role store.Role, out, errOut io.Writer) int {
 		fmt.Fprintf(out, "account %q removed\n", *name)
 		return 0
 	case "list":
+		// Holding the admin key means the caller is the human admin (full
+		// detail). An agent holds only EMCLI_KEY and gets a reduced JSON view.
+		_, adminErr := crypto.AdminKeyFromEnv()
+		isAdmin := adminErr == nil
 		accs, err := st.ListAccounts()
 		if err != nil {
-			fmt.Fprintf(errOut, "list: %v\n", err)
+			if isAdmin {
+				fmt.Fprintf(errOut, "list: %v\n", err)
+			} else {
+				_ = Failure(CodeDB, err.Error()).Write(out)
+			}
 			return 1
 		}
+		if !isAdmin {
+			items := make([]map[string]any, 0, len(accs))
+			for _, a := range accs {
+				items = append(items, map[string]any{
+					"name":     a.Name,
+					"from":     a.SendFrom(),
+					"can_send": a.Mode == "RW",
+				})
+			}
+			_ = Success(map[string]any{"accounts": items}).Write(out)
+			return 0
+		}
 		fmt.Fprintf(out, "%-16s %-4s %-28s %s\n", "NAME", "MODE", "IMAP", "USER")
 		for _, a := range accs {
 			fmt.Fprintf(out, "%-16s %-4s %-28s %s\n",