refactor: remove Python diffctx pipeline, Rust backend required

Author: nikolay-e

src/treemapper/__init__.py

@@ -5,7 +5,7 @@
 from pathlib import Path
 from typing import Any
 
-from .diffctx import ProjectGraph, build_diff_context, build_project_graph
+from .diffctx import build_diff_context, build_project_graph
 from .ignore import get_ignore_specs, get_whitelist_spec
 from .tree import TreeBuildContext, build_tree
 from .version import __version__
@@ -14,7 +14,6 @@
 logging.getLogger("treemapper").addHandler(logging.NullHandler())
 
 __all__ = [
-    "ProjectGraph",
     "__version__",
     "build_diff_context",
     "build_project_graph",

src/treemapper/diffctx/__init__.py

@@ -1,7 +1,17 @@
 from __future__ import annotations
 
+from typing import TYPE_CHECKING
+
 from .git import GitError
 from .pipeline import build_diff_context
-from .project_graph import ProjectGraph, build_project_graph
+
+if TYPE_CHECKING:
+    from .project_graph import ProjectGraph
 
 __all__ = ["GitError", "ProjectGraph", "build_diff_context", "build_project_graph"]
+
+
+def build_project_graph(*args, **kwargs):  # type: ignore[no-untyped-def]
+    from .project_graph import build_project_graph as _build
+
+    return _build(*args, **kwargs)