fix: exit codes match spec (0, 1, 2, 127) and silence usage on runtime errors

Exit 2 for missing required arguments, exit 127 for agent not found. SilenceUsage on all commands to avoid dumping usage on runtime errors.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/archive.go

@@ -11,10 +11,11 @@ import (
 )
 
 var archiveCmd = &cobra.Command{
-	Use:   "archive <query>",
-	Short: "Mark a workspace as archived",
-	Args:  cobra.ExactArgs(1),
-	RunE:  runArchive,
+	Use:          "archive <query>",
+	Short:        "Mark a workspace as archived",
+	Args:         cobra.ExactArgs(1),
+	SilenceUsage: true,
+	RunE:         runArchive,
 }
 
 func init() {

cmd/info.go

@@ -11,8 +11,9 @@ import (
 var infoCmd = &cobra.Command{
 	Use:   "info <query>",
 	Short: "Display metadata and path for a workspace",
-	Args:  cobra.ExactArgs(1),
-	RunE:  runInfo,
+	Args:         cobra.ExactArgs(1),
+	SilenceUsage: true,
+	RunE:         runInfo,
 }
 
 var infoAll bool

cmd/list.go

@@ -14,8 +14,9 @@ import (
 var listCmd = &cobra.Command{
 	Use:   "list",
 	Short: "Show recent workspaces in reverse-chronological order",
-	Args:  cobra.NoArgs,
-	RunE:  runList,
+	Args:         cobra.NoArgs,
+	SilenceUsage: true,
+	RunE:         runList,
 }
 
 var (

cmd/new.go

@@ -13,8 +13,9 @@ var newCmd = &cobra.Command{
 	Use:   "new [title]",
 	Short: "Create a new task workspace and launch the agent",
 	Long:  "Create a new task workspace and launch the agent. If title is omitted, generates task-HHMMSS.",
-	Args:  cobra.MaximumNArgs(1),
-	RunE:  runNew,
+	Args:         cobra.MaximumNArgs(1),
+	SilenceUsage: true,
+	RunE:         runNew,
 }
 
 var (

cmd/open.go

@@ -12,10 +12,11 @@ import (
 )
 
 var openCmd = &cobra.Command{
-	Use:   "open <query>",
-	Short: "Open a workspace directory without launching the agent",
-	Args:  cobra.ExactArgs(1),
-	RunE:  runOpen,
+	Use:          "open <query>",
+	Short:        "Open a workspace directory without launching the agent",
+	Args:         cobra.ExactArgs(1),
+	SilenceUsage: true,
+	RunE:         runOpen,
 }
 
 var openAll bool

cmd/resume.go

@@ -12,10 +12,11 @@ import (
 )
 
 var resumeCmd = &cobra.Command{
-	Use:   "resume <query>",
-	Short: "Reopen an existing workspace and launch the agent",
-	Args:  cobra.ExactArgs(1),
-	RunE:  runResume,
+	Use:          "resume <query>",
+	Short:        "Reopen an existing workspace and launch the agent",
+	Args:         cobra.ExactArgs(1),
+	SilenceUsage: true,
+	RunE:         runResume,
 }
 
 var (