feat(config): seed root symlink mappings before deep scanning

Add `_seed_root_symlink_mappings` method to ensure symlinked root folders are recorded before deep scanning, preventing them from being missed during directory traversal. This ensures that root symlinks are properly captured in the path mappings.

Additionally, normalize separators in relative paths for cross-platform consistency in `BaseModelService`, and update tests to verify root symlinks are preserved in the cache.

tests/config/test_symlink_cache.py

@@ -1,3 +1,4 @@
+import json
 import os
 
 import pytest
@@ -143,3 +144,40 @@ def test_background_rescan_refreshes_cache(monkeypatch: pytest.MonkeyPatch, tmp_
     new_real = _normalize(os.path.realpath(new_target))
     assert second_cfg._path_mappings.get(new_real) == _normalize(str(dir_link))
     assert second_cfg.map_path_to_link(str(new_target)) == _normalize(str(dir_link))
+
+
+def test_symlink_roots_are_preserved(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    settings_dir = tmp_path / "settings"
+    real_loras = tmp_path / "loras_real"
+    real_loras.mkdir()
+    loras_link = tmp_path / "loras_link"
+    loras_link.symlink_to(real_loras, target_is_directory=True)
+
+    checkpoints_dir = tmp_path / "checkpoints"
+    checkpoints_dir.mkdir()
+    embedding_dir = tmp_path / "embeddings"
+    embedding_dir.mkdir()
+
+    def fake_get_folder_paths(kind: str):
+        mapping = {
+            "loras": [str(loras_link)],
+            "checkpoints": [str(checkpoints_dir)],
+            "unet": [],
+            "embeddings": [str(embedding_dir)],
+        }
+        return mapping.get(kind, [])
+
+    monkeypatch.setattr(config_module.folder_paths, "get_folder_paths", fake_get_folder_paths)
+    monkeypatch.setattr(config_module, "standalone_mode", True)
+    monkeypatch.setattr(config_module, "get_settings_dir", lambda create=True: str(settings_dir))
+    monkeypatch.setattr(config_module.Config, "_schedule_symlink_rescan", lambda self: None)
+
+    cfg = config_module.Config()
+
+    normalized_real = _normalize(os.path.realpath(real_loras))
+    normalized_link = _normalize(str(loras_link))
+    assert cfg._path_mappings[normalized_real] == normalized_link
+
+    cache_path = settings_dir / "cache" / "symlink_map.json"
+    payload = json.loads(cache_path.read_text(encoding="utf-8"))
+    assert payload["path_mappings"][normalized_real] == normalized_link