add buildbot extension for autoscaling nix builders

buildbot-ext/pyproject.toml

@@ -0,0 +1,43 @@
+[build-system]
+requires = ["setuptools>=68", "wheel"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "buildbot-autoscale-ext"
+version = "0.1.0"
+description = "Buildbot extension for nix-builder-autoscaler capacity gating"
+requires-python = ">=3.12"
+dependencies = [
+    "buildbot",
+    "twisted",
+]
+
+[dependency-groups]
+dev = [
+    "pytest",
+    "ruff",
+    "pyright",
+]
+
+[tool.uv.extra-build-dependencies]
+py-ubjson = ["setuptools"]
+
+[tool.ruff]
+target-version = "py312"
+line-length = 100
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "UP", "B", "SIM", "ANN"]
+ignore = []
+
+[tool.ruff.lint.per-file-ignores]
+"*/tests/*" = ["ANN"]
+
+[tool.pyright]
+pythonVersion = "3.12"
+typeCheckingMode = "standard"
+include = ["buildbot_autoscale_ext"]
+exclude = ["**/tests"]
+
+[tool.pytest.ini_options]
+testpaths = ["buildbot_autoscale_ext/tests"]