reorganized build directory

build/common/bootstrap.py

@@ -0,0 +1,15 @@
+"""Ensure ``build/`` is importable as the root for ``common``, ``wheel``, and ``gui``."""
+
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+_BUILD_ROOT = Path(__file__).resolve().parents[1]
+
+
+def ensure_build_root_on_path() -> Path:
+    root = str(_BUILD_ROOT)
+    if root not in sys.path:
+        sys.path.insert(0, root)
+    return _BUILD_ROOT