Upgrade agentic workflows and enable prerelease auto-upgrades

[Copilot]

Upgrade the repository’s agentic workflows to gh-aw v0.88.4 and automatically track future prereleases.

Changes

• Recompiled all agentic workflows with gh-aw v0.88.4.
• Applied current workflow codemods and refreshed action/container pins.
• Added a weekly auto-upgrade workflow configured to include prereleases:

"auto_upgrade": {
  "cron": "0 9 * * 1",
  "options": ["--pre-releases"]
}