Update release/2026.8 with latest changes from main (#26203)

Fast-forwards the release branch with the latest main change, updating
the stable pipeline to consume PET from release/2026.12. The extension
version remains 2026.8.0.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: edvilme

build/azure-pipeline.stable.yml

@@ -144,7 +144,7 @@ extends:
           project: 'Monaco'
           definition: 593
           buildVersionToDownload: 'latestFromBranch'
-          branchName: 'refs/heads/release/2026.8'
+          branchName: 'refs/heads/release/2026.12'
           targetPath: '$(Build.SourcesDirectory)/python-env-tools/bin'
           artifactName: 'bin-$(buildTarget)'
           itemPattern: |