Install Mercurial on Windows runners via Chocolatey

Windows runners no longer ship with Mercurial pre-installed, causing
test failures. This commit adds Mercurial installation using Chocolatey
in the existing GnuPG setup step.

Changes:
- Add mercurial to the choco install command alongside gnupg
- Update step name to reflect it now installs both GnuPG and Mercurial
- Add explanatory comment about why Mercurial installation is needed

This uses a modern, declarative approach via the Chocolatey package
manager that's already in use for GnuPG installation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: RonnyPfannschmidt

.github/workflows/python-tests.yml

@@ -68,7 +68,7 @@ jobs:
           msystem: MINGW64
           install: git mingw-w64-x86_64-python mingw-w64-x86_64-python-setuptools
           update: true
-      - name: Setup GnuPG
+      - name: Setup GnuPG and Mercurial on Windows
         # At present, the Windows VMs only come with the copy of GnuPG that's bundled
         # with Git for Windows. If we want to use this version _and_ be able to set
         # arbitrary GnuPG home directories, then the test would need to figure out when
@@ -84,11 +84,15 @@ jobs:
         # Additionally, we'll explicitly set `gpg.program` to ensure Git for Windows
         # doesn't invoke the bundled GnuPG, otherwise we'll run into
         # <https://dev.gnupg.org/T5504>. See also: <https://dev.gnupg.org/T3020>.
+        #
+        # Windows runners no longer ship with Mercurial pre-installed, so we install
+        # it via Chocolatey using the 'hg' package.
         run: |
           $env:PATH = "C:\Program Files\Git\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\ProgramData\Chocolatey\bin"
           [Environment]::SetEnvironmentVariable("Path", $env:PATH, "Machine")
-          choco install gnupg -y --no-progress
+          choco install gnupg hg -y --no-progress
           echo "C:\Program Files (x86)\gnupg\bin" >> $env:GITHUB_PATH
+          echo "C:\Program Files\Mercurial\" >> $env:GITHUB_PATH
           git config --system gpg.program "C:\Program Files (x86)\gnupg\bin\gpg.exe"
         if: runner.os == 'Windows'
       - run: uv sync --group test --group docs --extra rich