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/wallpaper.rs

@@ -0,0 +1,17 @@
+use std::path::Path;
+use std::process::Command;
+
+use anyhow::{Context, Result, bail};
+
+pub fn apply(path: &Path) -> Result<()> {
+    let status = Command::new("awww")
+        .arg("set")
+        .arg(path)
+        .status()
+        .context("failed to run awww — is awww-daemon running?")?;
+
+    if !status.success() {
+        bail!("awww set exited with {}", status);
+    }
+    Ok(())
+}