Fully support all mention kinds (#36134)

Feature parity with the agent1 @mention kinds:
- File
- Symbols
- Selections
- Threads
- Rules
- Fetch


Release Notes:

- N/A

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Co-authored-by: Cole Miller <cole@zed.dev>
389d24d7e5Agus Zubiaga committed on 8/13/2025, 8:11:32 PM· committed by GitHubparent389d382
17 files changedLine totals unavailable