Perception system emits DirectObservation/LeftLOS knowledge events
based on snapshot visibility. Entities entering LOS get Direct
confidence; leaving LOS downgrades to KnowsDetails. System params
are optional for backward compatibility when KnowledgePlugin is not
registered. 28 knowledge graph unit tests included.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Implement direction-dependent visibility modulation per D-015.
Forward cone (~120 deg) at full range, peripheral (~180 deg each side)
at reduced range, blind spot (~60 deg behind) excluded. Facing component
updated on player movement via facing_from_delta.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>