Minor cleanups: gitignore out/, expect() messages, comment wording

- .gitignore: ignore the /out/ ISO build dir
- bos-settings: use expect() with messages over unwrap() for piped stdio;
  drop a stray blank line
- pacman.conf: reword the SigLevel=Never TODO as a future-improvement note

bos-settings/src/ui/views/breadbar.rs

@@ -6,7 +6,6 @@ fn css_path() -> PathBuf {
     crate::config::config_dir().join("breadbar/style.css")
 }
 
-
 pub fn build() -> GBox {
     let path = css_path();
     let existing_css = std::fs::read_to_string(&path).unwrap_or_default();

bos-settings/src/ui/views/packages.rs

@@ -50,9 +50,10 @@ fn stream_command(args: &[&str], log_buf: gtk4::TextBuffer) {
             }
         };
 
-        // Merge stderr into the channel too
-        let stdout = child.stdout.take().unwrap();
-        let stderr = child.stderr.take().unwrap();
+        // Merge stderr into the channel too.
+        // Both are Some because we spawned with Stdio::piped() above.
+        let stdout = child.stdout.take().expect("stdout piped");
+        let stderr = child.stderr.take().expect("stderr piped");
 
         let tx2 = sender.clone();
         std::thread::spawn(move || {