Adds the mention-like inline context to developer chat.
Adds models and their columns to dev chat for rill developer context. This is the 1st iteration, we will probably add more of these.

Known issue: Using keyboard to move to model doesnt automatically uncollapse it because the options are not loaded. Will do a follow up that does some significant changes to the highlight manager in a separate PR.

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!