facade: corrupted raw email addresses when they include multiple `@` signs

> [!NOTE]
> Migrated from [augurlabs/augur#3791](https://github.com/augurlabs/augur/issues/3791)
> Originally opened by `@MoralCode` on 2026-03-25

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When doing some scripting to correct facade data, I discovered that, in https://github.com/chaoss/augur commit 36aab5bcce6ba96ee4539c967c0672d489e24e99, andrew's email address was set to `andrew@root@chaoss.tv`, however, Augur, for both the raw and parsed values for committer and author email are `andrew@root`.

While this likely isnt an issue for `cmt_author_email` (which should probably conform to at least some expectations of syntax validity), the `cmt_author_raw_email` value is the same, suggesting the error is happening earlier in the processing.

This was found as a result of trying out libgit2 as a backend for git #258