Accept a UTF-8 BOM at the start of lightcraft-cli --script files

Fixes #2937

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

apps/lightcraft-cli/src/main.rs

@@ -557,6 +557,8 @@ fn run(args: &[String]) -> Result<(), String> {
         } else {
             std::fs::read_to_string(path).map_err(|e| format!("{path}: {e}"))?
         };
+        // Windows PowerShell 5.1 writes a UTF-8 BOM; it is not part of the first JSON line.
+        let text = text.strip_prefix('\u{feff}').unwrap_or(&text);
         for (n, line) in text.lines().enumerate().filter(|(_, l)| !l.trim().is_empty() && !l.trim_start().starts_with('#')) {
             let v: Value = serde_json::from_str(line).map_err(|e| format!("{path}:{}: {e}", n + 1))?;
             // `{"command": id, "params": …}` or a control request `{"method": m, "params": …}`
@@ -851,6 +853,8 @@ fn snapshot(args: &[String]) -> Result<(), String> {
     let mut failed = 0usize;
     if let Some(script) = &script {
         let text = std::fs::read_to_string(script).map_err(|e| format!("{script}: {e}"))?;
+        // Windows PowerShell 5.1 writes a UTF-8 BOM; it is not part of the first JSON line.
+        let text = text.strip_prefix('\u{feff}').unwrap_or(&text);
         let mut out = std::io::stdout().lock();
         for (n, line) in text.lines().enumerate() {
             let line = line.trim();

apps/lightcraft-cli/tests/it/cli.rs

@@ -506,6 +506,20 @@ fn run_cli(args: &[&str], stdin: Option<&str>) -> (bool, Vec<Value>, String) {
     (o.status.success(), lines, String::from_utf8_lossy(&o.stderr).to_string())
 }
 
+/// Windows PowerShell 5.1 writes a UTF-8 BOM; `--script` (file and stdin) must accept it.
+#[test]
+fn run_script_accepts_a_utf8_bom() {
+    let text = "\u{feff}{\"command\": \"library.info\", \"params\": {}}\n";
+    let script = tmp("bom-steps.jsonl");
+    std::fs::write(&script, text).unwrap();
+    let (ok, lines, err) = run_cli(&["--demo", "--script", script.to_str().unwrap()], None);
+    assert!(ok, "file: {err}");
+    assert_eq!(lines.len(), 1, "{lines:?}");
+    let (ok, lines, err) = run_cli(&["--demo", "--script", "-"], Some(text));
+    assert!(ok, "stdin: {err}");
+    assert_eq!(lines.len(), 1, "{lines:?}");
+}
+
 #[test]
 fn run_subcommand_chains_commands_and_persists_a_library() {
     let input = tmp("run-in.png");