## Summary
This is a non-behavior-changing refactor to follow-up
https://github.com/astral-sh/ruff/pull/9321 by modifying
`DisplayParseError` to use owned data and make it useable as a
standalone error type (rather than using references and implementing
`Display`). I don't feel very strongly either way. I thought it was
awkward that the `FormatCommandError` had two branches in the display
path, and wanted to represent the `Parse` vs. other cases as a separate
enum, so here we are.
## Summary
I always found it odd that we had to pass this in, since it's really
higher-level context for the error. The awkwardness is further evidenced
by the fact that we pass in fake values everywhere (even outside of
tests). The source path isn't actually used to display the error; it's
only accessed elsewhere to _re-display_ the error in certain cases. This
PR modifies to instead pass the path directly in those cases.
## Summary
This PR refactors the `NotebookIndex` struct to use `OneIndexed` to make
the
intent of the code clearer.
## Test Plan
Update the existing test case and run `cargo test` to verify the change.
- [x] Verify `--diff` output
- [x] Verify the diagnostics output
- [x] Verify `--show-source` output
