ci: add FFmpeg preflight workflow and helpers

src-tauri/src/bin/check_ffmpeg.rs

@@ -0,0 +1,13 @@
+fn main() {
+    // Call the library's FFmpeg preflight check used by the application.
+    match radio_tauri_lib::player::preflight_ffmpeg_only() {
+        Ok(()) => {
+            println!("FFmpeg preflight OK");
+            std::process::exit(0);
+        }
+        Err(e) => {
+            eprintln!("FFmpeg preflight failed: {}", e);
+            std::process::exit(2);
+        }
+    }
+}