Pure math, no React, no scene access. Three primitives plus a facade:
- `snapScalar(value, step)` / `snapPointToGrid(point, step)` /
`snapVec3ToGrid(point, step)` — regular grid snapping. Default
step 0.25m matches the editor's wall tool.
- `snapPointToAngle(from, cursor, angleStep, gridStep?)` — locks a
cursor to the nearest angle multiple from a fixed point, preserves
distance, optionally re-grids the projected point. Default angle
step π/12 (15°).
- `snapAngleToList(angle, list, tolerance)` — snaps a free angle to
the nearest entry in a fixed list (e.g. 0/45/90/135) within a
tolerance; returns the original angle otherwise. Handles wrap.
- `snapServices` facade — `grid.*` + `angle.*` namespaces. Stable
contract that `DragAction.snap` callbacks receive. Phase 3 ports
the existing `snapWallDraftPoint` family from
`editor/.../wall-drafting.ts` under a `wall.*` namespace.
17 unit tests cover the math + the facade pass-through. No existing
callers re-wired yet — Phase 2 column/shelf tools are the first
consumers.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
