Add BCR-2026-010: Fair Witness Predicates

Proposes Known Values for neutral observer attestation: observerWitness,
observationTimestamp, observerIndependence, observationScope, etc.

Community range 1120-1124. Seeking rough consensus; willing to use
100000+ if community prefers.

Signed-off-by: Christopher Allen <ChristopherA@LifeWithAlacrity.com>

Author: ChristopherA