feat: Add 'spawn' as alias for 'start' subcommand across roles

Added 'spawn' as an alias for 'start' in the following commands:
- gt witness start → also gt witness spawn
- gt refinery start → also gt refinery spawn
- gt deacon start → also gt deacon spawn
- gt crew start → also gt crew spawn

This improves discoverability since agents are guessing 'spawn'
when trying to start roles.

Note: gt polecat does not have a 'start' command - polecat spawning
is handled via 'gt sling'.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/crew.go

@@ -241,6 +241,7 @@ var crewPrevCmd = &cobra.Command{
 
 var crewStartCmd = &cobra.Command{
 	Use:     "start <rig> [name]",
+	Aliases: []string{"spawn"},
 	Short:   "Start crew worker(s) in a rig",
 	Long: `Start crew workers in a rig, creating workspaces if they don't exist.
 

internal/cmd/deacon.go

@@ -40,6 +40,7 @@ and check status.`,
 
 var deaconStartCmd = &cobra.Command{
 	Use:     "start",
+	Aliases: []string{"spawn"},
 	Short:   "Start the Deacon session",
 	Long: `Start the Deacon tmux session.
 

internal/cmd/refinery.go

@@ -35,6 +35,7 @@ into integration branches and ultimately to main.`,
 
 var refineryStartCmd = &cobra.Command{
 	Use:     "start [rig]",
+	Aliases: []string{"spawn"},
 	Short:   "Start the refinery",
 	Long: `Start the Refinery for a rig.
 

internal/cmd/witness.go

@@ -39,6 +39,7 @@ that seem blocked, and reports status to the mayor.`,
 
 var witnessStartCmd = &cobra.Command{
 	Use:     "start <rig>",
+	Aliases: []string{"spawn"},
 	Short:   "Start the witness",
 	Long: `Start the Witness for a rig.