feat(config): replace symlink scanning with cached mapping system

- Add `get_settings_dir` import for cache directory resolution
- Replace `_scan_symbolic_links` and `_rebuild_preview_roots` with unified `_initialize_symlink_mappings` method
- Implement fingerprint-based cache validation using root mtimes, inodes, and noise-aware timestamps
- Add helper methods for path normalization, cache location, and symlink root aggregation
- Improve performance by avoiding redundant symlink traversal when directory structure is unchanged

tests/config/test_symlink_cache.py

@@ -0,0 +1,111 @@
+import os
+
+import pytest
+
+from py import config as config_module
+
+
+def _normalize(path: str) -> str:
+    return os.path.normpath(path).replace(os.sep, "/")
+
+
+def _setup_paths(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    settings_dir = tmp_path / "settings"
+    loras_dir = tmp_path / "loras"
+    loras_dir.mkdir()
+    checkpoint_dir = tmp_path / "checkpoints"
+    checkpoint_dir.mkdir()
+    embedding_dir = tmp_path / "embeddings"
+    embedding_dir.mkdir()
+
+    def fake_get_folder_paths(kind: str):
+        mapping = {
+            "loras": [str(loras_dir)],
+            "checkpoints": [str(checkpoint_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))
+
+    return loras_dir, settings_dir
+
+
+def test_symlink_scan_skips_file_links(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    loras_dir, settings_dir = _setup_paths(monkeypatch, tmp_path)
+
+    target_dir = loras_dir / "target"
+    target_dir.mkdir()
+    dir_link = loras_dir / "dir_link"
+    dir_link.symlink_to(target_dir, target_is_directory=True)
+
+    file_target = loras_dir / "model.safetensors"
+    file_target.write_text("content", encoding="utf-8")
+    file_link = loras_dir / "file_link"
+    file_link.symlink_to(file_target)
+
+    cfg = config_module.Config()
+
+    normalized_target_dir = _normalize(os.path.realpath(target_dir))
+    normalized_link_dir = _normalize(str(dir_link))
+    assert cfg._path_mappings[normalized_target_dir] == normalized_link_dir
+
+    normalized_file_real = _normalize(os.path.realpath(file_target))
+    assert normalized_file_real not in cfg._path_mappings
+
+    cache_path = settings_dir / "cache" / "symlink_map.json"
+    assert cache_path.exists()
+
+
+def test_symlink_cache_reuses_previous_scan(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    loras_dir, settings_dir = _setup_paths(monkeypatch, tmp_path)
+
+    target_dir = loras_dir / "target"
+    target_dir.mkdir()
+    dir_link = loras_dir / "dir_link"
+    dir_link.symlink_to(target_dir, target_is_directory=True)
+
+    first_cfg = config_module.Config()
+    cached_mappings = dict(first_cfg._path_mappings)
+    cache_path = settings_dir / "cache" / "symlink_map.json"
+    assert cache_path.exists()
+
+    def fail_scan(self):
+        raise AssertionError("Cache should bypass directory scan")
+
+    monkeypatch.setattr(config_module.Config, "_scan_symbolic_links", fail_scan)
+
+    second_cfg = config_module.Config()
+    assert second_cfg._path_mappings == cached_mappings
+    assert second_cfg.map_path_to_link(str(target_dir)) == _normalize(str(dir_link))
+
+
+def test_symlink_cache_survives_noise_mtime(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    loras_dir, settings_dir = _setup_paths(monkeypatch, tmp_path)
+
+    target_dir = loras_dir / "target"
+    target_dir.mkdir()
+    dir_link = loras_dir / "dir_link"
+    dir_link.symlink_to(target_dir, target_is_directory=True)
+
+    recipes_dir = loras_dir / "recipes"
+    recipes_dir.mkdir()
+    noise_file = recipes_dir / "touchme.txt"
+
+    first_cfg = config_module.Config()
+    cache_path = settings_dir / "cache" / "symlink_map.json"
+    assert cache_path.exists()
+
+    # Update a noisy path to bump parent directory mtime
+    noise_file.write_text("hi", encoding="utf-8")
+
+    def fail_scan(self):
+        raise AssertionError("Cache should bypass directory scan despite noise mtime")
+
+    monkeypatch.setattr(config_module.Config, "_scan_symbolic_links", fail_scan)
+
+    second_cfg = config_module.Config()
+    assert second_cfg.map_path_to_link(str(target_dir)) == _normalize(str(dir_link))