feat(tidy3d): Mutable attrs bypass _json_string cache, causing stale hashes and exports

- change hashing to md5

Jira: FXC-3374

Author: marcorudolphflex

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 - Improved performance of antenna metrics calculation by utilizing cached wave amplitude calculations instead of recomputing wave amplitudes for each port excitation in the `TerminalComponentModelerData`.
 - Fixed: In `Tidy3dBaseModel` the hash (and cached `.json_string`) are now sensitive to changes in `.attrs`.
+- Changed hashing method in `Tidy3dBaseModel` from sha256 to md5.
 
 ### Fixed
 - More robust `Sellmeier` and `Debye` material model, and prevent very large pole parameters in `PoleResidue` material model.

tidy3d/components/base.py

@@ -174,7 +174,7 @@ def _hash_self(self) -> str:
         """Hash this component with ``hashlib`` in a way that is the same every session."""
         bf = io.BytesIO()
         self.to_hdf5(bf)
-        return hashlib.sha256(bf.getvalue()).hexdigest()
+        return hashlib.md5(bf.getvalue()).hexdigest()
 
     def __init__(self, **kwargs):
         """Init method, includes post-init validators."""