fix: Add PowerShell to PATH for Windows runner

The arduino/setup-protoc action requires PowerShell to be in the PATH
on Windows. Add it explicitly for Windows runners.

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

Co-Authored-By: Claude <[email protected]>
Signed-off-by: Joe Isaacs <[email protected]>

Author: joseph-isaacs

.github/actions/setup-rust/action.yml

@@ -50,6 +50,11 @@ runs:
       shell: bash
       run: echo "PATH=$PATH" >> $GITHUB_ENV
 
+    - name: Add PowerShell to PATH (Windows)
+      if: runner.os == 'Windows'
+      shell: bash
+      run: echo "C:\Windows\System32\WindowsPowerShell\v1.0" >> $GITHUB_PATH
+
     - name: Install Protoc (for lance-encoding build step)
       uses: arduino/setup-protoc@v3
       with: