Use PDM instead of pip-tools to manage venv

Replace use of pip-tools to set up and maintain a Python virtual
environment (currently, only on macOS) with PDM. In addition to
supporting more modern Python conventions, including dependency groups
(which reduces the number of files involved in managing the venv), PDM
strives to be platform agnostic and should allow us to perform lock file
updates once (or at least from a single platform), rather than having to
separately update lock files for every supported platform.

.gitignore

@@ -27,5 +27,8 @@
 # Platform artifacts generated by `install_prereqs`
 /gen/
 
+# Local Python venv artifacts
+/.pdm-python
+
 # User-specified configuration
 /user.bazelrc

pyproject.toml

@@ -0,0 +1,29 @@
+[project]
+name = "drake"
+version = "1.36.0"
+description = "Default template for PDM package"
+authors = [
+    {name = "Drake Development Team", email = "drake-users@mit.edu"},
+]
+requires-python = ">=3.10"
+readme = "README.md"
+license = {text = "BSD-3-Clause"}
+dependencies = [
+    "ipywidgets",
+    "matplotlib",
+    "notebook",
+    "Pillow",
+    "pydot",
+    "PyYAML",
+]
+
+[dependency-groups]
+test = [
+    "flask",
+    "six",
+    "u-msgpack-python",
+    "websockets",
+]
+
+[tool.pdm]
+distribution = false

setup/BUILD.bazel

@@ -11,9 +11,6 @@ exports_files([
     "mac/source_distribution/Brewfile",
     "mac/source_distribution/Brewfile-doc-only",
     "mac/source_distribution/Brewfile-maintainer-only",
-    "mac/source_distribution/requirements.txt",
-    "mac/source_distribution/requirements-maintainer-only.txt",
-    "mac/source_distribution/requirements-test-only.txt",
     "ubuntu/binary_distribution/packages-jammy.txt",
     "ubuntu/source_distribution/packages-jammy.txt",
     "ubuntu/source_distribution/packages-jammy-clang.txt",