fix(tmux): use NewSessionWithCommand to avoid send-keys race condition

Agent sessions would fail on startup because send-keys arrived before the
shell was ready, causing 'bad pattern' and 'command not found' errors.

Fix: Create sessions with the command directly using tmux new-session's
command argument. This runs the agent as the pane's initial process,
avoiding shell readiness timing issues entirely.

Updated all agent managers: mayor, deacon, witness, refinery, polecat, crew.

Also fixes pre-existing build error in polecat/manager.go (polecatPath →
clonePath/newClonePath).

Closes #280

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

internal/polecat/manager.go

@@ -281,7 +281,7 @@ func (m *Manager) AddWithOptions(name string, opts AddOptions) (*Polecat, error)
 
 	// Copy overlay files from .runtime/overlay/ to polecat root.
 	// This allows services to have .env and other config files at their root.
-	if err := rig.CopyOverlay(m.rig.Path, polecatPath); err != nil {
+	if err := rig.CopyOverlay(m.rig.Path, clonePath); err != nil {
 		// Non-fatal - log warning but continue
 		fmt.Printf("Warning: could not copy overlay files: %v\n", err)
 	}
@@ -538,7 +538,7 @@ func (m *Manager) RepairWorktreeWithOptions(name string, force bool, opts AddOpt
 	}
 
 	// Copy overlay files from .runtime/overlay/ to polecat root.
-	if err := rig.CopyOverlay(m.rig.Path, polecatPath); err != nil {
+	if err := rig.CopyOverlay(m.rig.Path, newClonePath); err != nil {
 		fmt.Printf("Warning: could not copy overlay files: %v\n", err)
 	}
 
@@ -787,9 +787,9 @@ func (m *Manager) loadFromBeads(name string) (*Polecat, error) {
 
 // setupSharedBeads creates a redirect file so the polecat uses the rig's shared .beads database.
 // This eliminates the need for git sync between polecat clones - all polecats share one database.
-func (m *Manager) setupSharedBeads(polecatPath string) error {
+func (m *Manager) setupSharedBeads(clonePath string) error {
 	townRoot := filepath.Dir(m.rig.Path)
-	return beads.SetupRedirect(townRoot, polecatPath)
+	return beads.SetupRedirect(townRoot, clonePath)
 }
 
 // CleanupStaleBranches removes orphaned polecat branches that are no longer in use.

internal/polecat/session_manager.go

@@ -168,8 +168,19 @@ func (m *SessionManager) Start(polecat string, opts SessionStartOptions) error {
 		return fmt.Errorf("ensuring runtime settings: %w", err)
 	}
 
-	// Create session
-	if err := m.tmux.NewSession(sessionID, workDir); err != nil {
+	// Build startup command first
+	command := opts.Command
+	if command == "" {
+		command = config.BuildPolecatStartupCommand(m.rig.Name, polecat, m.rig.Path, "")
+	}
+	// Prepend runtime config dir env if needed
+	if runtimeConfig.Session != nil && runtimeConfig.Session.ConfigDirEnv != "" && opts.RuntimeConfigDir != "" {
+		command = config.PrependEnv(command, map[string]string{runtimeConfig.Session.ConfigDirEnv: opts.RuntimeConfigDir})
+	}
+
+	// Create session with command directly to avoid send-keys race condition.
+	// See: https://github.com/anthropics/gastown/issues/280
+	if err := m.tmux.NewSessionWithCommand(sessionID, workDir, command); err != nil {
 		return fmt.Errorf("creating session: %w", err)
 	}
 
@@ -205,24 +216,6 @@ func (m *SessionManager) Start(polecat string, opts SessionStartOptions) error {
 	agentID := fmt.Sprintf("%s/%s", m.rig.Name, polecat)
 	debugSession("SetPaneDiedHook", m.tmux.SetPaneDiedHook(sessionID, agentID))
 
-	// Send initial command with env vars exported inline
-	command := opts.Command
-	if command == "" {
-		command = config.BuildPolecatStartupCommand(m.rig.Name, polecat, m.rig.Path, "")
-	}
-	// Prepend runtime config dir env if needed
-	if runtimeConfig.Session != nil && runtimeConfig.Session.ConfigDirEnv != "" && opts.RuntimeConfigDir != "" {
-		command = config.PrependEnv(command, map[string]string{runtimeConfig.Session.ConfigDirEnv: opts.RuntimeConfigDir})
-	}
-	// Wait for shell to be ready before sending keys (prevents "can't find pane" under load)
-	if err := m.tmux.WaitForShellReady(sessionID, 5*time.Second); err != nil {
-		_ = m.tmux.KillSession(sessionID)
-		return fmt.Errorf("waiting for shell: %w", err)
-	}
-	if err := m.tmux.SendKeys(sessionID, command); err != nil {
-		return fmt.Errorf("sending command: %w", err)
-	}
-
 	// Wait for Claude to start (non-fatal)
 	debugSession("WaitForCommand", m.tmux.WaitForCommand(sessionID, constants.SupportedShells, constants.ClaudeStartTimeout))