Flaky Copilot Chat Sanity Test

[vritant24]

https://dev.azure.com/monacotools/Monaco/_build/results?buildId=434921&view=logs&j=15ec5277-fdc6-550c-b203-acb65f44f31c&t=120c9214-43d4-5761-6dc9-d5e173c65e37

[ulugbekna]

Likely the same upstream flake as #312131. #319695 bumps sanity-suite retries to 2 (3 attempts total) and adds a describeOutcome() diagnostic helper that prints item count, part names, currentProgress, result.errorDetails, and result.metadata.responseId in every assertion so future failures should be both rarer and easier to triage.message