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### Before submitting

- [ ] This PR targets the `develop` branch.
- [ ] I searched for an existing PR or issue covering the same change.
- [ ] My contribution is licensed under the Boost Software License 1.0.

### Type of change

- [ ] Bug fix
- [ ] New feature or API addition
- [ ] Refactor (no behavior change)
- [ ] Documentation
- [ ] Build, CI, or tooling
- [ ] Other (specify below)

### Does this PR introduce a breaking change?

- [ ] Yes (describe migration impact below)
- [ ] No

### What this PR does

<!-- A short summary of the change. -->

### Motivation

<!-- Why is this needed? Link related issue with `Fixes #N` or `Refs #N`. -->

### Testing

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How did you verify the change? Which compilers and standard libraries did
you build against? Were new tests added under `test/`?
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### Checklist

- [ ] Existing tests pass (`b2` in the `test/` directory).
- [ ] New behavior is covered by a test, or this is a docs / build / refactor change.
- [ ] Documentation was updated if user-facing behavior changed.
- [ ] No new compiler warnings on the platforms I built against.
