assistant_context_editor: Register `ContextEditor` actions that were lost (#30428)

This PR restores the `ContextEditor` actions that were lost in
https://github.com/zed-industries/zed/pull/30168.

Closes https://github.com/zed-industries/zed/issues/30356.

Release Notes:

- agent: Added back some missing actions, including `assistant: quote
selection`.
e13ecc07bcMarshall Bowers committed on 5/9/2025, 7:59:44 PM· committed by GitHubparentbef25c7
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