Split out from #17110

Indent multiline error messages properly, and add test since it wasn't captured previously.

Split out from #17110

Indent multiline error messages properly, and add a test with a
multiline context and a context below since that combination isn't
captured atm.

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Co-authored-by: Zanie Blue <contact@zanie.dev>

This adds abstractions for handing hints, pulling them out of ad-hoc
addendums to error messages and treating them as a first-class concept
so we can render them more consistently.

The key concepts are:

- `Hints`: a wrapper struct for `Vec<Cow<'a, str>>`
- `Hint`: a trait with `hints(&self) -> Hints<'_>`

Error types now `impl Hint` to provide hints. This means errors need to
carry more information to construct the `Hint` lazily instead of ahead
of time. The majority of refactoring around error types is to support
that change.

When displaying errors, we
[downcast](https://github.com/astral-sh/uv/pull/18090/changes#r2935662966)
to each type known to implement the trait and extract hints. We then
display all the hints after the error chain is complete.

The user-facing affect of this is that hints are now always rendered
outside the error chain.

This is a blocker to #17110 and is pulled out of that project. There is
still some weirdness with miette's `help:` prompts that will be removed
entirely in a following change.

---------

Co-authored-by: Codex <noreply@openai.com>

Keep `ExitStatus` code-only and represent propagated command errors
explicitly as `UvError::User` or `UvError::Unexpected`. Command handlers
classify and propagate their errors; the entrypoint renders user errors
as a single line with exit code 1 and renders unclassified error chains
with exit code 2. This preserves the existing default text and exit
codes while providing a behavior-focused alternative to the
error-carrying `ExitStatus` introduced in #20114.

The stacked follow-up #20163 routes this centralized rendering through
`Printer` and defines the resulting `-q` and `-qq` behavior.

Part of #17110.

Render final `UvError` values through `Printer` at the command
entrypoint. The default error-chain renderer accepts the `Printer`
directly and owns hint collection and stream selection; `-q` preserves
final errors and `-qq` suppresses them while exit codes remain 1 for
user errors and 2 for unexpected errors. Stacked on #20188.

Part of #17110.
Closes #19326.

Render `UvError::User` with the standard error-chain renderer instead of
formatting only the outer message. This preserves causal context while
retaining exit code 1 and the existing printer behavior: `-q` preserves
the error and `-qq` suppresses it. The stacked #20160 relies on this to
preserve the cause of an invalid `--with` requirement. Part of #17110.

Classify invalid `uv tool run --with` requirements as `UvError::User` so
the entrypoint owns final rendering and exit-status selection instead of
printing a local miette report. The expected error retains exit code 1
and its full cause chain. Builds on the user-error renderer from #20217.

Part of #17110.