Fix opening chat editors

[mjbvz]

Looks like multiple changes are using the chat editor input uri type to instead of the session uri. This fixes new chat editor but I think a few other callers are doing the same thing. Will follow up with separate PRs

Not 100% sure why this only recently started happening since the changes have been in multiple weeks but this fix is the correct modern way to do this

[Copilot]

Pull request overview

This PR fixes an issue where chat editor opening actions were incorrectly using editor input URIs instead of session URIs. The fix adds a new helper method to generate session URIs and updates the "New Chat Editor" and "New Chat Window" actions to use it.

Changes:

• Added LocalChatSessionUri.getNewSessionUri() helper method to generate new session URIs
• Updated "New Chat Editor" action to use session URI instead of editor input URI
• Updated "New Chat Window" action to use session URI instead of editor input URI

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/vs/workbench/contrib/chat/common/model/chatUri.ts	Added getNewSessionUri() helper method that generates a new local chat session URI with a random handle
src/vs/workbench/contrib/chat/browser/actions/chatActions.ts	Updated imports to include ACTIVE_GROUP and LocalChatSessionUri, and modified two action implementations to use LocalChatSessionUri.getNewSessionUri() with proper group targeting