Photoshop's Vertical, Horizontal, Dual Axis and Diagonal paint symmetry presets beside the
path-based symmetry: axes start at the document centre, Transform Symmetry moves and rotates
them (Shift snaps to 15°, Enter applies, Esc cancels), and all copies merge into one coverage
pass so overlaps don't build opacity. New paint.setSymmetry command and preset icons. Fixes#1648.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
