Copilot Fix(CI Failure): Bump pinned Copilot CLI default to 1.0.83

[github-actions]

The scheduled version-pin-drift job caught that our pinned default fell one patch release behind — turns out even version numbers need to keep up with the Joneses.

https://github.com/austenstone/copilot-cli/actions/runs/34197807759/job/Compare%20pinned%20default%20against%20registry%20latest#step:3

💥 Error Log

Run PINNED=$(python3 -c "import yaml;print(yaml.safe_load(open('action.yml'))['inputs']['copilot-version']['default'])")
LATEST=$(npm view --registry=https://registry.npmjs.org '@github/copilot@latest' version)
##[warning]copilot-version default is pinned to 1.0.80 but @latest is 1.0.83
##[error]Process completed with exit code 1.

🕵️‍♂️ Diagnosis

action.yml pins inputs.copilot-version.default to 1.0.80. The version-pin-drift job (added in #81) runs on a schedule and fails whenever this pinned default no longer matches @github/copilot@latest on npm, to catch stale pins before they go unnoticed. npm now publishes 1.0.83, so the check failed as designed — this is not a code regression, just an expected drift alert.

🛠️ Proposed Fix

Bump the pinned default from 1.0.80 to 1.0.83 in action.yml, and update the matching examples/table in README.md for consistency. Verified locally that re-running the exact drift-check script now reports pinned=1.0.83 latest=1.0.83 (match).