Add token usage breakdowns to the show command

[sg4tech]

Summary

• Add show --by model|project|token-type token breakdowns.
• Support top-N aggregation with an explicit other row.
• Add typed warehouse contracts, SQLite querying, renderers, CLI wiring, and documentation.
• Preserve project scope and worktree grouping behavior.

Testing

• Added CLI parser and warehouse breakdown tests covering ranking, scoping, token types, and top-N aggregation.