Redesign pgconsole icon as a faceted triangular window frame

Replace the window glyph with an equilateral triangle split into three
trapezoid shards with mitred seams and a hollow centre triangle (the
screen), sharing one blue gradient — same triangle base shape and
faceted, hollow-centre language as pgparser and pgtui. Drop the unused
stale pgconsole.png raster.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: tianzhou