0.48.0 — binaural spatial path

Binaural recordings (declared 2-channel ear signals) now get spatial estimates instead of a refusal: a lateral azimuth from the interaural time difference (GCC-PHAT over the DOA band, Woodworth-limited to ±90°, + = left) and a diffuseness from delay-compensated interaural magnitude coherence, which is invariant to per-channel linear filtering and therefore survives the HRTF. Level differences between the ears are treated as head colouring, never direction; elevation and the intensity vector remain undefined, as they must for ear signals.

Also fixes the session README recording note, which fell through to the AmbiX text for binaural sessions.

Motivated by a three-recorder soundwalk comparison (H3-VR binaural and stereo decodes vs a phone) where the binaural decode was the best-sounding and least analysable file of the trio. Seven new tests; 525 green.