fix: use x-access-token form for GitHub App token git push

[ramsessanchez]

Summary

Fixes the weekly generation pipelines failing to git push after the PAT was removed from ADO, following the move to GitHub App auth (#3657).

Root cause

GitHub App installation tokens must authenticate as the password with the username x-access-token:

https://x-access-token:<token>@github.com/owner/repo.git

The previous form — https://<token>@github.com/... — puts the token in the username position with no password. That works for a PAT (which is why pushes succeeded while the PAT still existed in ADO), but an installation token in that position is rejected, so git falls back to prompting for a password and fails non-interactively:

The value of the GITHUB_TOKEN environment variable is being used for authentication.
fatal: Cannot prompt because user interactivity has been disabled.
fatal: could not read Password for 'https://***@github.com': terminal prompts disabled

Fix

Prefixed all five pipeline push URLs with x-access-token::

• common-templates/create-pr.yml
• common-templates/download-openapi-docs.yml
• generation-templates/generate-command-metadata.yml
• weekly-examples-update.yml
• command-metadata-refresh.yml

The x-access-token:<token> form is also valid for PATs, so this is backward compatible. gh pr create was unaffected (it uses GITHUB_TOKEN via the REST API, not a git URL).

Note: This pull request was created with assistance from GitHub Copilot.