Use CPU-only PyTorch index to speed up dev dependency installation

torch and torchvision are transitive dependencies of vws-python-mock.
By default uv resolves them from PyPI, which provides CUDA-enabled wheels
on Linux (~916 MB for torch). Redirecting to the pytorch CPU-only index
reduces torch to ~189 MB — a 727 MB saving per cold-cache install.

Following: https://vws-python.github.io/vws-python-mock/installation.html#faster-installation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: adamtheturtle

pyproject.toml

@@ -74,6 +74,11 @@ optional-dependencies.dev = [
     "sphinx-substitution-extensions==2026.1.12",
     "sphinxcontrib-spelling==8.0.2",
     "sybil==9.3.0",
+    # Listed explicitly (despite being transitive via vws-python-mock) so that
+    # [tool.uv.sources] can redirect to the CPU-only PyTorch index.
+    # See: https://vws-python.github.io/vws-python-mock/installation.html#faster-installation
+    "torch>=2.5.1",
+    "torchvision>=0.20.1",
     "ty==0.0.17",
     "types-requests==2.32.4.20260107",
     "vulture==2.14",
@@ -106,6 +111,11 @@ bdist_wheel.universal = true
 # Code to match this is in ``conf.py``.
 version_scheme = "post-release"
 
+[tool.uv]
+sources.torch = { index = "pytorch-cpu" }
+sources.torchvision = { index = "pytorch-cpu" }
+index = [ { name = "pytorch-cpu", url = "https://download.pytorch.org/whl/cpu", explicit = true } ]
+
 [tool.ruff]
 line-length = 79
 lint.select = [
@@ -277,6 +287,13 @@ pep621_dev_dependency_groups = [
     "dev",
     "release",
 ]
+# torch and torchvision are listed explicitly in dev deps to allow
+# [tool.uv.sources] to redirect them to the CPU-only PyTorch index,
+# but they are not directly imported in the vws-python source code.
+per_rule_ignores.DEP002 = [
+    "torch",
+    "torchvision",
+]
 
 [tool.pyproject-fmt]
 indent = 4