Use plain truthiness for fused_projections assertions
`fused_projections` is a plain bool -- the only tri-state around it,
`_native_fused_projections`, is gone -- so `is True` and `is False` only add
noise. The file used both forms and a bare `not`; it now uses one.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
