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/role_test.go

@@ -9,16 +9,22 @@ import (
 )
 
 func TestCommandRole(t *testing.T) {
-	admin := []string{"account", "whitelist", "config", "audit"}
-	agent := []string{"list", "get", "search", "ack", "send", "doctor"}
-	for _, c := range admin {
+	adminCmds := [][]string{
+		{"whitelist"}, {"config"}, {"audit"},
+		{"account"}, {"account", "add"}, {"account", "edit"}, {"account", "remove"},
+	}
+	agentCmds := [][]string{
+		{"list"}, {"get"}, {"search"}, {"ack"}, {"send"}, {"doctor"},
+		{"account", "list"},
+	}
+	for _, c := range adminCmds {
 		if commandRole(c) != store.RoleAdmin {
-			t.Errorf("%s should be admin", c)
+			t.Errorf("%v should be admin", c)
 		}
 	}
-	for _, c := range agent {
+	for _, c := range agentCmds {
 		if commandRole(c) != store.RoleAgent {
-			t.Errorf("%s should be agent", c)
+			t.Errorf("%v should be agent", c)
 		}
 	}
 }