release: Bump extension version to 2026.8.0 (#26199)

Bumps the extension to the 2026.8.0 stable release version and updates
the stable pipeline to consume PET from release/2026.8. The VS Code
pre-release pipeline is expected to reject the even version temporarily;
main will return to 2026.9.0-dev in the follow-up PR after the release
branch is cut.

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/2026.4'
+          branchName: 'refs/heads/release/2026.8'
           targetPath: '$(Build.SourcesDirectory)/python-env-tools/bin'
           artifactName: 'bin-$(buildTarget)'
           itemPattern: |

package-lock.json

@@ -2,7 +2,7 @@
     "name": "python",
     "displayName": "Python",
     "description": "Python language support with extension access points for IntelliSense (Pylance), Debugging (Python Debugger), linting, formatting, refactoring, unit tests, and more.",
-    "version": "2026.7.0-dev",
+    "version": "2026.8.0",
     "featureFlags": {
         "usingNewInterpreterStorage": true
     },