Remove physicsnemo compatibility layer

.importlinter

@@ -9,14 +9,11 @@ contract_types =
 name = Prevent Upward Imports in the PhysicsNemo Structure
 type = layers
 exhaustive = True
-ignore_imports =
-   physicsnemo -> physicsnemo.compat
 exhaustive_ignores =
    conftest
 containers=
    physicsnemo
 layers = 
-   compat
    experimental
    deploy | active_learning | diffusion | sym
    models : datapipes : metrics : domain_parallel : optim

CHANGELOG.md

@@ -65,6 +65,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Removed
 
+- Removes the opt-in `physicsnemo.compat` import-alias layer and the
+  `PHYSICSNEMO_ENABLE_COMPAT` environment variable. The layer mapped pre-v2.0
+  module paths onto their v2.0 locations; three minor releases later, callers
+  should import from the current paths listed in `v2.0-MIGRATION-GUIDE.md`.
+  Checkpoint loading is unaffected.
 - Removes `physicsnemo.utils.mesh`, deprecated since 2.1 with removal scheduled
   for 2.2. The `vtk` and `stl` entries leave the `utils-extras` extra with it.
   Replacements:

physicsnemo/__init__.py

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import os
-
 # This is to ensure warp is quiet at startup:
 import warp as wp
 
@@ -25,18 +23,3 @@
 wp.config.log_level = wp.LOG_WARNING
 
 __version__ = "2.3.0a0"
-
-
-# Backwards-compatibility is opt-in. Enable with env var or via enable_compat().
-if os.getenv("PHYSICSNEMO_ENABLE_COMPAT") in {
-    "1",
-    "true",
-    "True",
-    "YES",
-    "yes",
-    "on",
-    "ON",
-}:
-    from .compat import install as _compat_install
-
-    _compat_install()

skills/physicsnemo-discover/references/RECIPES.md

@@ -156,8 +156,8 @@ Grep -n "^class <ClassName>" physicsnemo/ --type py
 # 7b. Search by function name
 Grep -n "^def <func_name>" physicsnemo/ --type py
 
-# 7c. If not found where expected — check compat layer for renames
-Read physicsnemo/compat/__init__.py
+# 7c. If not found where expected — check the rename tables for moved paths
+Grep -n "<ClassName>" v2.0-MIGRATION-GUIDE.md CHANGELOG.md
 ```
 
 If a name isn't found anywhere, it may have been renamed. Do not emit it.