fix(agent): register --id flag on agent deploy

deployAgent resolves the agent via getAgentID, which reads cmd.String("id"),
but the deploy subcommand never registered the --id flag (unlike config, status,
restart, rollback). As a result `lk agent deploy --id CA_XXX` failed at parse time
with "flag provided but not defined: --id".

Add idFlag(false) to the deploy command's flags, matching the other subcommands.

Fixes #830

Author: mcdgavin

cmd/lk/agent.go

@@ -221,6 +221,7 @@ var (
 					Before: createAgentClient,
 					Action: deployAgent,
 					Flags: []cli.Flag{
+						idFlag(false),
 						secretsFlag,
 						secretsFileFlag,
 						secretsMountFlag,

cmd/lk/agent_test.go

@@ -456,3 +456,21 @@ func TestRequireSecrets_QuietSuppressesStatus(t *testing.T) {
 		})
 	}
 }
+
+// TestAgentDeployRegistersIDFlag is a regression test for #830: `lk agent deploy`
+// resolves the agent via getAgentID, which reads cmd.String("id"). The deploy
+// subcommand must therefore register the --id flag; it previously omitted it, so
+// `lk agent deploy --id ...` failed at flag-parse time with "flag provided but not defined".
+func TestAgentDeployRegistersIDFlag(t *testing.T) {
+	agentCmd := findCommandByName(AgentCommands, "agent")
+	require.NotNil(t, agentCmd, "top-level 'agent' command must exist")
+
+	deployCmd := findCommandByName(agentCmd.Commands, "deploy")
+	require.NotNil(t, deployCmd, "'agent deploy' command must exist")
+
+	var names []string
+	for _, f := range deployCmd.Flags {
+		names = append(names, f.Names()...)
+	}
+	require.Contains(t, names, "id", "'agent deploy' must register the --id flag")
+}