Merge PR #602: fix: prevent data loss in clipboard PNG conversion when ImageMagick fails

Authored by 0xbyt4. Only deletes temp .bmp after confirmed successful conversion, restores original on failure. Adds 3 tests.

hermes_cli/clipboard.py

@@ -292,9 +292,12 @@ def _convert_to_png(path: Path) -> bool:
             ["convert", str(tmp), "png:" + str(path)],
             capture_output=True, timeout=5,
         )
-        tmp.unlink(missing_ok=True)
         if r.returncode == 0 and path.exists() and path.stat().st_size > 0:
+            tmp.unlink(missing_ok=True)
             return True
+        else:
+            # Convert failed — restore the original file
+            tmp.rename(path)
     except FileNotFoundError:
         logger.debug("ImageMagick not installed — cannot convert BMP to PNG")
         if tmp.exists() and not path.exists():