prompt: remove newline heuristic from exec prompt

All array entries in prompt config are now shell commands.
Removes the special case that treated entries with newlines as literal text.

pkg/agent/prompt_resolver.go

@@ -41,11 +41,6 @@ func resolveExecPrompt(cmds []string, cwd string) (string, error) {
 		if cmdStr == "" {
 			continue
 		}
-		// Entries containing a newline are literal text, not commands.
-		if strings.Contains(cmdStr, "\n") {
-			parts = append(parts, cmdStr)
-			continue
-		}
 		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 		cmd := exec.CommandContext(ctx, "sh", "-c", cmdStr)
 		if cwd != "" {