fix: eliminate TOCTOU race in yamlio.load_yaml()

Remove exists() pre-check and catch FileNotFoundError from read_text()
to provide a clear BundlerError even under race conditions.

Author: Quratulain-bilal

src/specify_cli/bundler/lib/yamlio.py

@@ -54,10 +54,10 @@ def load_yaml(path: Path) -> Any:
     caller to reject.
     """
     path = Path(path)
-    if not path.exists():
-        raise BundlerError(f"File not found: {path}")
     try:
         text = path.read_text(encoding="utf-8")
+    except FileNotFoundError:
+        raise BundlerError(f"File not found: {path}") from None
     except (OSError, UnicodeError) as exc:
         # A non-UTF-8 file raises UnicodeDecodeError, which is a ValueError --
         # NOT an OSError -- so it escaped this module's "IO failures degrade