Dropped the Mountain terrain def and extended Forest to maxHeight 1.01, so the
former mountain elevations generate forest instead. No terrain blocks light now;
the occluder mechanism stays generic (mature trees still cast shadows) -- updated
the stale "mountain" comments. Removed the unused terrain.mountain localization.
Build + --check-content clean.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>