`Repo.ignored` runs `git check-ignore -- <paths>` and recovered the
matched paths from stdout with
`.replace("\\\\", "\\").replace('"', "").split("\n")`. git C-quotes a
path that contains a non-ASCII byte (with the default `core.quotePath`),
a double quote, a backslash or a control character, and that replacement
does not reverse the quoting. With `*.env` in `.gitignore`:

- `données.env` came back as `donn\303\251es.env`
- `q"uote.env` came back as `q\uote.env`
- `tab<TAB>.env` came back as `tab\t.env`
- a name containing a line feed came back with a literal `\n`

A caller that compares the result with the paths it passed in, for
example to leave ignored files out of a commit, an upload or an archive,
therefore treats those ignored files as not ignored.

Read stdout as bytes and unquote each quoted line with
`git.diff._unquote_path`, which already reverses git's C-quoting for
patch headers. Splitting at line feeds stays safe because git always
quotes a path that contains one. `git check-ignore -z` would avoid the
quoting, but git accepts `-z` only together with `--stdin`. Paths git
does not quote are returned unchanged.

Adds `test_ignored_items_reported_verbatim` to `test/test_repo.py`; it
fails before this change and passes after. `ruff check`,
`ruff format --check` and `mypy` pass. The full pytest suite run locally
fails the same 83 tests with and without this change; those failures
come from fixture commits missing in the local clone, not from this
change.