Initial implementation of breadpaper

CLI tool that sets a wallpaper with awww, generates a pywal colour
palette, and reloads bread-theme to recolour all running bread GTK apps.
Includes CI workflows, bakery metadata, and Arch PKGBUILD.

src/lib.rs

@@ -0,0 +1,61 @@
+mod pywal;
+mod theme;
+mod wallpaper;
+
+use std::path::{Path, PathBuf};
+
+use anyhow::{Context, Result, bail};
+
+const IMAGE_EXTENSIONS: &[&str] = &["png", "jpg", "jpeg", "webp", "gif", "bmp"];
+
+pub fn set(path: &Path) -> Result<()> {
+    let path = validate(path)?;
+    apply_wallpaper(&path)?;
+    generate_palette(&path)?;
+    reload_theme()?;
+    Ok(())
+}
+
+pub fn get() -> Result<PathBuf> {
+    let home = std::env::var("HOME").context("HOME not set")?;
+    let wal_file = PathBuf::from(home).join(".cache/wal/wal");
+
+    let contents = std::fs::read_to_string(&wal_file)
+        .with_context(|| format!("no wallpaper set yet ({})", wal_file.display()))?;
+
+    Ok(PathBuf::from(contents.trim()))
+}
+
+pub fn apply_wallpaper(path: &Path) -> Result<()> {
+    wallpaper::apply(path)
+}
+
+pub fn generate_palette(path: &Path) -> Result<()> {
+    pywal::generate(path)
+}
+
+pub fn reload_theme() -> Result<()> {
+    theme::reload()
+}
+
+fn validate(path: &Path) -> Result<PathBuf> {
+    let canonical = path
+        .canonicalize()
+        .with_context(|| format!("not found: {}", path.display()))?;
+
+    let ext = canonical
+        .extension()
+        .and_then(|e| e.to_str())
+        .unwrap_or("")
+        .to_lowercase();
+
+    if !IMAGE_EXTENSIONS.contains(&ext.as_str()) {
+        bail!(
+            "unsupported file type '.{}' — expected one of: {}",
+            ext,
+            IMAGE_EXTENSIONS.join(", ")
+        );
+    }
+
+    Ok(canonical)
+}