The polygon-draft snap path used the legacy model: bypassSnap = shiftPressed and
angleSnap = pointCount > 0 && !bypassSnap, so the 15deg angle lock engaged after
the first vertex regardless of mode — hijacking grid/lines/off into angle-snap
even though the HUD chip showed the right mode.
Migrate all three placement paths (move preview, single-click vertex, double-
click close) to the unified model: angleSnap = isAngleSnapActive(); grid flows
through snapToHalf (step 0 in non-grid modes); wall-snap/alignment already gates
on isMagneticSnapActive(). Behavior now matches the chip — grid quantizes,
angles locks 15deg rays, lines snaps to walls/alignment, off is free. Drop the
now-dead bypassSnap param from snapPolygonDraftPoint.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
