feat(crew): auto-prime when exec'ing Claude in-session

When running `gt crew at <name>` from inside the target session, we exec
Claude directly. Previously this meant we couldn't send `gt prime` afterward.

Now we pass "gt prime" as the initial prompt argument to the Claude CLI,
so Claude loads context immediately upon startup.

Closes gt-qivm

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

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

internal/cmd/crew_at.go

@@ -133,8 +133,9 @@ func runCrewAt(cmd *cobra.Command, args []string) error {
 	// Check if we're already in the target session
 	if isInTmuxSession(sessionID) {
 		// We're in the session at a shell prompt - just start Claude directly
+		// Pass "gt prime" as initial prompt so Claude loads context immediately
 		fmt.Printf("Starting Claude in current session...\n")
-		return execClaude()
+		return execClaude("gt prime")
 	}
 
 	// Attach to session using exec to properly forward TTY

internal/cmd/crew_helpers.go

@@ -147,7 +147,8 @@ func isShellCommand(cmd string) bool {
 
 // execClaude execs claude, replacing the current process.
 // Used when we're already in the target session and just need to start Claude.
-func execClaude() error {
+// If prompt is provided, it's passed as the initial prompt to Claude.
+func execClaude(prompt string) error {
 	claudePath, err := exec.LookPath("claude")
 	if err != nil {
 		return fmt.Errorf("claude not found: %w", err)
@@ -155,6 +156,9 @@ func execClaude() error {
 
 	// exec replaces current process with claude
 	args := []string{"claude", "--dangerously-skip-permissions"}
+	if prompt != "" {
+		args = append(args, prompt)
+	}
 	return syscall.Exec(claudePath, args, os.Environ())
 }