Repackage exercise: remove `sdk` from package name only

[edburns]

During week 2026-21 at the latest, @SteveSandersonMS lead the Copilot SDK team to a decision to remove "sdk" from the "package name" type concept for all the languages. The rationale is that it's obvious you're in an SDK when you're working with code. Also, we observed that the other languages had rpc where Java has json.

Here is the mapping for Java.

• com.github.copilot.sdk → com.github.copilot .
• com.github.copilot.sdk.json → com.github.copilot.rpc .

GitHub internal issue https://github.com/github/copilot-sdk-partners/issues/115 .