Fix NextFontIssue IssueStage: CodeGen → Resolve (#92588)
### What?
Changes `NextFontIssue`'s `IssueStage` from `CodeGen` to `Resolve`.
### Why?
`NextFontIssue` is emitted during font resolution — when validating font
configuration options (`util.rs`) and when fetching/resolving Google
Font metadata (`google/mod.rs`, `google/font_fallback.rs`). None of
these occur during code generation; they all happen at the resolve stage
of the build pipeline.
Using `IssueStage::CodeGen` was incorrect and caused these font issues
to be grouped/sorted with code generation errors rather than resolution
errors. The local-font counterpart (`FontResolvingIssue` in
`next_font/local/mod.rs`) already correctly uses `IssueStage::Resolve`.
### How?
Single-line fix: change `IssueStage::CodeGen.cell()` to
`IssueStage::Resolve.cell()` in the `stage()` method of `impl Issue for
NextFontIssue`.
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Co-authored-by: Tobias Koppers <sokra@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
