This PR factors some more code related to the `RecentBuffersContext` out
of the `AssistantPanel` and into the corresponding module.
We're trying to strike a balance between keeping this code easy to
evolve as we work on the Assistant, while also having some semblance of
separation/structure.
This also adds the missing functionality of updating the remaining token
count when the `CurrentProjectContext` is enabled/disabled.
Release Notes:
- N/A
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Co-authored-by: Max <max@zed.dev>
Marshall BowersandMax
66e873942d