The headroom provider the add-band guard consumes (task #120 defines the seam; this is
the REAL provider satisfying it — #120's own default is always-allow-under-cap, so the
integrator swaps that default for this). A plain zero-argument function so the guard
carries no dependency on the engine: each call polls the source and assesses fresh.
The headroom provider the add-band guard consumes (task #120 defines the seam; this is the REAL provider satisfying it — #120's own default is always-allow-under-cap, so the integrator swaps that default for this). A plain zero-argument function so the guard carries no dependency on the engine: each call polls the source and assesses fresh.