Configure cost and quality in Copilot auto model selection

📋 Developer Action Items

• ☐ Diff the official changelog for GitHub / Copilot before you bump — APIs, defaults, and removed flags only.
• ☐ Install through the vendor's documented channel in staging; keep a one-command rollback and time-box the canary.
• ☐ Grep your repo for old flag names, lockfile pins, and plugin versions that the notes mark as breaking.
• ☐ Prefer the first patch cut over the day-zero tag unless you have a reason to be on the leading edge.
• ☐ If GitHub Changelog did not name a region, plan, or SKU, screenshot the official availability line before you promise it to users.