Implement BiRefNet and HAT Sharper models with background removal capabilities

- Added validation documentation for AI model tiers.
- Introduced `background.py` for background removal logic, including inference functions for alpha and foreground extraction.
- Created `onnx_birefnet.py` to handle BiRefNet model sessions and alpha inference.
- Developed tests for background models, ensuring proper dispatch and session reuse.
- Added tests for BiRefNet ONNX model to validate alpha output and error handling for invalid values.
- Implemented model export scripts for BiRefNet and HAT Sharper, ensuring proper weight compression and licensing.
- Created `deform_sampling.py` for deformable convolution operations used in BiRefNet.
- Added utility functions for compressing ONNX weights without altering graph arithmetic.
- Introduced a reference plane node for depth field adjustments in geometry processing.

tests/tools/models/test_cli.py

@@ -50,10 +50,10 @@ def test_valid_model_cache_skips_all_preparation():
 
 
 @pytest.mark.parametrize("valid", [True, False])
-def test_pisa_export_validates_all_outputs_before_replacing(tmp_path, valid):
+def test_isolated_export_validates_all_outputs_before_replacing(tmp_path, valid):
     module = load_sync_models()
     digest = module.hashlib.sha256(b"new").hexdigest()
-    models = tuple(module.ModelFile("PISA_SR", "pisa-sr", name, 3, digest) for name in ("a.onnx", "b.onnx"))
+    models = tuple(module.ModelFile("HAT_GAN_X4_SHARPER", "hat-gan-x4-sharper", name, 3, digest) for name in ("a.onnx", "b.onnx"))
 
     def export(command, **kwargs):
         destination = Path(command[-1])
@@ -71,7 +71,7 @@ def test_pisa_export_validates_all_outputs_before_replacing(tmp_path, valid):
                 module.prepare_model(models[0])
             assert not models[0].destination.exists()
             assert models[1].destination.read_bytes() == b"old"
-        assert not list(tmp_path.glob(".pisa-sr-*"))
+        assert not list(tmp_path.glob(".hat-gan-x4-sharper-*"))
 
 
 def test_local_export_failure_cleans_temporary_output(tmp_path):
@@ -120,7 +120,7 @@ class SyncModelsTests(unittest.TestCase):
         builds = self.sync.MODEL_BUILDS
         self.assertEqual(
             set(builds),
-            {"REALESRGAN_GENERAL_WDN_X4V3", "SAFMN_REAL_X4"},
+            {"REALESRGAN_GENERAL_WDN_X4V3"},
         )
         for build in builds.values():
             self.assertTrue(build.source_url.startswith("https://github.com/"))