editor: snapping overhaul — shared-wall rooms, deterministic slab elevation, cursor-true transfers (#458)

* fix(snapping): show alignment lines in all modes, snap only in lines; north export; R/T hint; grid default

- Alignment guides display in every snapping mode (grid/lines/angles/off);
  magnetic pull applies only in 'lines'. New isAlignmentGuideActive() predicate
  decouples guide display from the snap delta across all placement/move/draw
  producers (item, wall, fence, slab/ceiling/roof, column/shelf/spawn, door/
  window, MEP, 2D floorplan drafting, surface snap).
- Floorplan PDF export now rotates to north-up (FLOORPLAN_VIEW_ROTATION_DEG -
  building rotation), matching the on-screen aligned-to-north view.
- Item placement rotate hint collapsed to a single 'R / T  Rotate' row.
- Default item snapping mode changed lines -> grid.

* feat(walls): detect rooms across shared walls + tight connect-snap in all modes

Room detection: planarize the wall graph before face-finding — split straight
walls at T-junctions where another wall ends mid-span, so a room closed against
the middle of an existing wall is detected, not just isolated 4-wall rooms.

Auto-close: wire the wall builder's "Room (auto-close)" to the same room graph
via wallClosesRoom(), so drafting stops when a segment seals a room against the
existing structure — not only when the chain returns to its own start.

Connectivity snap: add a tight wall-connect snap (WALL_CONNECT_SNAP_RADIUS 0.05)
that also runs in grid/off/angles — within range of a wall (body or corner,
uniform radius) the endpoint sticks onto it and the beacon shows, so rooms close
in every mode. Lines keeps its wider magnetic radii. Gate alignment guides in
non-magnetic modes to the same connect distance so a corner dot no longer
magnetises the cursor from far.

Tests: cover T-junction detection + wallClosesRoom; update the item-default and
wall-split tests for the mode-driven behaviour.

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

* feat(surfaces): gate alignment guides to connect distance in non-magnetic modes

Port the wall drafting/endpoint gating to the shared slab/ceiling/roof snap
(resolveSurfacePlanPointSnap): in grid/off/angles, only anchors within the
connect distance are fed to the alignment resolver, so guides form to nearby
points and far corner dots stop lighting up from across the plan. Filtering the
candidates (local-frame, like the cursor) rather than the resolved guides avoids
the floor-plan view rotation baked into the guide coords. Lines mode keeps the
full-range guides; the surface wall connect-snap is unaffected.

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

* fix(slabs): deterministic wall-slab overlap via clipped overlap length

Wall elevation used ray-cast point samples that landed exactly on the
slab boundary for perpendicular walls, so whether a butting wall
followed the slab's elevation depended on which side of the slab it
touched. Clip the wall centerline and face lines against the polygon
and require >=5cm of on/inside length instead: walls along the slab
edge follow it on every side, point contact never does.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(grid): lift lattice 1mm off slab tops; wall-align on wall-item move start

The horizontal snap lattice sat exactly at the followed surface Y, so it
z-fought elevated slab tops while moving items. The visual mesh now rides
1mm above; the grid event plane keeps the true height.

Moving a wall-hosted item showed a horizontal grid until the first
pointer move published a wall surface — the mesh fallback assumed UP.
Derive the host wall normal from the item mesh's world orientation
(local +Z faces out of the wall) so the lattice is wall-aligned from
the first frame.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* feat(editor): unify selection shortcuts + truthful select-mode hints

Shift+click now toggles selection membership in 3D like Cmd/Ctrl (and
appends on box-select release), matching the 2D floorplan. The HUD rows
describe what actually works in both views: move is plain left-drag (the
grip/dot), the two vague selection rows collapse into one Cmd/Shift
or-group, and the modifier-held variants (freely / with guides / bypass
snaps) are gone — guides follow the snapping mode now. Key pills join
with + for combos and / for alternatives; Shift renders as the shift
icon.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(editor): group gizmos — reliable rotate grabs, mutual hide, snapping-mode integration

The group-rotate gizmo never received pointer events through the shared
invisible hit-area path (EDITOR_LAYER + custom raycast) in its portalled
context; its handlers now live on the visible arrow plus a plain
default-layer invisible torus, so hover and drag work with a fat target.

Group drags begin a handle-drag scope: each gizmo hides while its
sibling drags (the frozen corner goes stale), idle hints leave the HUD,
and the drag gets contextual hints — Shift free-rotation for rotate, the
snapping chips for move.

Group move joins the snapping-mode system via the 'item' context: Shift
cycles the mode, Ctrl the grid step (both read live mid-drag), and
'lines' runs the same Figma-style alignment as single-node moves against
the group's bbox anchors. Chip clicks now tick like the keyboard cycles.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(editor): group-move ticks in every snapping mode

Mirror the single-node move's sfx: emit per delta change rather than
only on grid crossings, so lines/off get the same rate-limited texture.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(items): keep host transfers glued to the cursor

Moving between hosts used to diverge from the pointer and mangle state:

- Grab offsets: every surface anchor (wall / ceiling / shelf / item
  surface / floor) preserved the grab offset by re-seeding from the
  item's carried-over position on each new host, landing it far from
  the cursor. The grab offset now survives only on the original host
  and only until the item anchors anywhere else — after that every
  host (the original included) centers the item under the cursor.
  Applied uniformly to the placement coordinator and the window/door
  move tools.

- Rotation: detaching from a rotated shelf/table back to the floor kept
  the HOST-local yaw as the level yaw, visibly spinning the item. The
  detach now re-expresses the item's world yaw in the level frame.

- Elevation: the same detach wrote the level parentId to the store but
  not the draft ref, so the floor-elevation resolver bailed on its
  parent-must-be-a-level guard — the snap grid and the item stopped
  following slab elevations for the rest of the drag.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(items): latch grab-offset forgetting across every host kind

Review follow-up (PR #458): unify the per-surface grab-forget rule into
one grabForgotten latch. A wall/ceiling item could not actually reach a
shelf or the floor (item-surface enter rejects attachTo assets), but a
wall item CAN anchor on a roof face — and returning to its original
wall then restored the stale grab offset. Roof-wall transitions (and
floor landings after a host visit) now trip the latch in the
coordinator and the window/door move tools alike.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

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

packages/nodes/src/item/definition.ts

@@ -316,8 +316,7 @@ export const itemDefinition: NodeDefinition<typeof ItemNode> = {
 
   toolHints: [
     { key: 'Left click', label: 'Place item' },
-    { key: 'R', label: 'Rotate counterclockwise' },
-    { key: 'T', label: 'Rotate clockwise' },
+    { key: 'R / T', label: 'Rotate' },
     { key: 'Shift', label: 'Cycle snapping mode' },
     { key: 'Alt', label: 'Force place' },
     { key: 'Esc', label: 'Cancel' },

packages/nodes/src/item/floorplan-move.ts

@@ -283,7 +283,8 @@ function buildFloorItemSession(
     apply({ planPoint }) {
       const gridSnapped = resolvePlanPoint(planPoint)
       // Figma-style alignment layered on the grid snap, mode-driven (matching 3D):
-      // guides only resolve/snap when magnetic (lines) mode is active.
+      // guides are DISPLAYED in every snapping mode; the magnetic pull onto them
+      // is applied only in "lines" mode (`applySnap`).
       const { point: snapped } = applyFloorplanAlignment(
         gridSnapped,
         movingFootprintAnchors(
@@ -293,7 +294,7 @@ function buildFloorItemSession(
           rotationY,
         ),
         candidates,
-        { bypass: !isMagneticSnapActive() },
+        { applySnap: isMagneticSnapActive() },
       )
 
       const sourceY = node.position[1]