Language Service does not detect schema changes

> Re-raising this as an ADS parity/migration gap.
>
> This is effectively the same scenario tracked in Azure Data Studio issue #194:
> https://github.com/microsoft/azuredatastudio/issues/194
>
> The core problem is still schema drift: after creating new tables, columns, or other objects, IntelliSense can continue using stale metadata and falsely mark valid objects as invalid until the cache is refreshed manually.
>
> The Refresh IntelliSense Cache command is a useful workaround, but it is not a substitute for automatic or opportunistic drift detection.
>
> Recent related discussion:
> https://github.com/microsoft/vscode-mssql/issues/21704
>
> It would be useful to treat this issue as the umbrella item for automatic schema drift detection / metadata refresh so newly created objects stop showing false IntelliSense errors without requiring manual intervention.

_Originally posted by @aasimkhan30 in [#311](https://github.com/microsoft/vscode-mssql/issues/311#issuecomment-4218334891)_

Start with the linked Azure Data Studio issue #194 and recent discussion in #21704, then inspect how the Refresh IntelliSense Cache command relates to the reported behavior. The work is done when newly created tables, columns, and other objects no longer produce false IntelliSense errors without manual cache refresh.

Written by the indexing model from the issue text.