fix(io): remove released edit lock files

Closes #579

src/io/edit_lock.rs

@@ -134,7 +134,13 @@ impl EditLease {
         );
         let _ = sidecar.flush();
 
-        let (drawing, platform_warning) = acquire_drawing_lock(&canonical)?;
+        let (drawing, platform_warning) = match acquire_drawing_lock(&canonical) {
+            Ok(lock) => lock,
+            Err(error) => {
+                let _ = std::fs::remove_file(&lock_path);
+                return Err(error);
+            }
+        };
         Ok(Self {
             _sidecar: sidecar,
             drawing,
@@ -162,6 +168,14 @@ impl EditLease {
     }
 }
 
+impl Drop for EditLease {
+    fn drop(&mut self) {
+        // Remove the path while the exclusive sidecar lock is still held so
+        // another editor cannot acquire it during cleanup.
+        let _ = std::fs::remove_file(&self.lock_path);
+    }
+}
+
 fn acquire_drawing_lock(path: &Path) -> Result<(Option<File>, Option<String>), EditLeaseError> {
     let drawing = match OpenOptions::new().read(true).write(true).open(path) {
         Ok(file) => file,