Fix prod-readiness issues flagged in audit

- Fix XDG config dir logic in config/mod.rs (was double-nesting and had /home/user hardcode)
- Replace /home/user hardcodes in breadbar.rs and hyprland.rs with config::config_dir()
- Fix /home/user hardcode in packages.rs (uses /root fallback for .local/state path)
- Remove eprintln! from GTK callback in packages.rs (no stderr at runtime)
- Fix YAML parse error in branding.desc (missing space after sidebarTextHighlight key)
- Add .gitignore (Rust target/, ISO artifacts, editor/OS junk, secrets)
- Delete state.rs (dead code — never mod'd in main.rs)
- Add brightnessctl, grim, slurp to packages.x86_64 (used by keybinds)
- Rename can-you-begin-a-composed-beacon.md → DESIGN.md

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bos-settings/src/config/mod.rs

@@ -15,10 +15,13 @@ pub fn save<T: serde::Serialize>(path: &Path, val: &T) -> Result<(), Box<dyn Err
 }
 
 pub fn config_dir() -> PathBuf {
-    let home = std::env::var("HOME").unwrap_or_else(|_| {
-        std::env::var("XDG_CONFIG_HOME")
-            .map(|p| PathBuf::from(p).parent().unwrap_or(Path::new("/")).to_string_lossy().to_string())
-            .unwrap_or_else(|_| "/home/user".to_string())
-    });
+    // Honour XDG_CONFIG_HOME if set; otherwise fall back to $HOME/.config.
+    if let Ok(xdg) = std::env::var("XDG_CONFIG_HOME") {
+        let p = PathBuf::from(xdg);
+        if p.is_absolute() {
+            return p;
+        }
+    }
+    let home = std::env::var("HOME").unwrap_or_else(|_| "/root".to_string());
     PathBuf::from(home).join(".config")
 }