## Summary
Resolves#15502.
`ty generate-shell-completion` now works in a similar manner to `ruff
generate-shell-completion`.
## Test Plan
Manually:
<details>
```shell
$ cargo run --package ty generate-shell-completion nushell
module completions {
# An extremely fast Python type checker.
export extern ty [
--help(-h) # Print help
--version(-V) # Print version
]
# ...
}
export use completions *
```
</details>