- [x] Basic implementation
- [x] Disable commit buttons when committing is not possible (empty
message, no changes)
- [x] Upgrade GitSummary to efficiently figure out whether there are any
staged changes
- [x] Make CommitAll work
- [x] Surface errors with toasts
  - [x] Channel shutdown
  - [x] Empty commit message or no changes
  - [x] Failed git operations
- [x] Fix added files no longer appearing correctly in the project panel
(GitSummary breakage)
- [x] Fix handling of commit message

Release Notes:

- N/A

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Co-authored-by: Nate <nate@zed.dev>