Merge origin/main into feat/placement-interaction-overhaul

Resolve 7 conflicts keeping our snapping migration + floorplan perf work as
source of truth, combined with main's MEP run-continuation / Alt-detach /
latch handles. Rebuilt two import blocks the auto-merge silently truncated
(node-arrow-handles.tsx, duct-fitting/move-tool.tsx).

Verified: tsc clean across core/viewer/editor/nodes/mcp, 451 tests pass,
biome clean. Floorplan view-transform re-render storm confirmed pre-existing
(not introduced by this merge).

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

packages/nodes/src/pipe-segment/move-tool.tsx

@@ -29,6 +29,7 @@ import {
   collectGhostAlignmentCandidates,
   resolveGhostAlignment,
 } from '../shared/ghost-alignment'
+import { type RunMoveConnectivity, startRunMoveConnectivity } from '../shared/run-move-connectivity'
 
 type Vec3 = [number, number, number]
 
@@ -137,6 +138,12 @@ export const MovePipeSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     }
     if (existedAtStart) setMeshHidden(true)
 
+    // Carry connected fittings (+ their other runs) as the whole run slides.
+    // Snapshot once at drag start; only existing runs are mated to anything.
+    const connectivity: RunMoveConnectivity | null = existedAtStart
+      ? startRunMoveConnectivity(node)
+      : null
+
     const setPreview = (path: Vec3[]) => {
       previewPathRef.current = path
       setPreviewPath(path)
@@ -176,7 +183,9 @@ export const MovePipeSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       }
       prevSnapRef.current = cur
       hasMovedRef.current = true
-      setPreview(originalPath.map(([x, y, z]) => [x + dx, y, z + dz] as Vec3))
+      const nextPath = originalPath.map(([x, y, z]) => [x + dx, y, z + dz] as Vec3)
+      setPreview(nextPath)
+      connectivity?.preview({ path: nextPath })
     }
 
     const commit = (event: GridEvent) => {
@@ -204,10 +213,21 @@ export const MovePipeSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
         useScene.getState().createNode(created as AnyNode, node.parentId as AnyNodeId)
         selectId = created.id as AnyNodeId
       } else {
-        useScene.getState().updateNode(nodeId, { path: finalPath } as Partial<AnyNode>)
+        // Fold connected-fitting / sibling-run follow-updates into the SAME
+        // batch as the moved run so the whole joint is one undo step.
+        const followUpdates = connectivity?.commitUpdates({ path: finalPath }) ?? []
+        useScene
+          .getState()
+          .updateNodes([
+            { id: nodeId, data: { path: finalPath } as Partial<AnyNode> },
+            ...followUpdates,
+          ])
         useScene.getState().markDirty(nodeId)
       }
       useScene.temporal.getState().pause()
+      // Followers are committed to the store — drop their live overrides so
+      // renderers read the canonical path/position.
+      connectivity?.clear()
       setMeshHidden(false)
 
       useAlignmentGuides.getState().clear()
@@ -219,6 +239,7 @@ export const MovePipeSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
     }
 
     const onCancel = () => {
+      connectivity?.clear()
       if (existedAtStart) {
         setMeshHidden(false)
         useViewer.getState().setSelection({ selectedIds: [nodeId] })
@@ -238,6 +259,7 @@ export const MovePipeSegmentTool: React.FC<{ node: AnyNode }> = ({ node }) => {
       emitter.off('grid:move', onMove)
       emitter.off('grid:click', commit)
       emitter.off('tool:cancel', onCancel)
+      connectivity?.clear()
       useAlignmentGuides.getState().clear()
       if (existedAtStart) setMeshHidden(false)
       useScene.temporal.getState().resume()

packages/nodes/src/pipe-segment/tool.tsx

@@ -59,6 +59,11 @@ import { pipeSegmentDefinition } from './definition'
  *   - Esc clears an anchored start point.
  */
 const PREVIEW_OPACITY = 0.55
+/** green-500 — the project's snap accent. The cursor ring + vertical line
+ *  recolour to this while the point is snapped onto an existing run / port,
+ *  so the coincidence reads with the familiar snap green (matches the duct
+ *  tool). */
+const SNAP_CURSOR_COLOR = '#22c55e'
 /** Nominal residential DWV sizes (inches). */
 const PIPE_DIAMETERS_IN = [1.25, 1.5, 2, 3, 4, 6] as const
 /** IPC default drain slope — ¼" per foot (1:48). */
@@ -92,6 +97,28 @@ function findNearbyPort(point: [number, number, number]): ScenePort | null {
   )
 }
 
+function pipeEndPort(pipe: PipeSegmentNode, id: 'start' | 'end'): ScenePort | null {
+  if (pipe.path.length < 2) return null
+  const index = id === 'start' ? 0 : pipe.path.length - 1
+  const neighborIndex = id === 'start' ? 1 : pipe.path.length - 2
+  const position = pipe.path[index]!
+  const neighbor = pipe.path[neighborIndex]!
+  const dx = position[0] - neighbor[0]
+  const dy = position[1] - neighbor[1]
+  const dz = position[2] - neighbor[2]
+  const len = Math.hypot(dx, dy, dz)
+  const direction: [number, number, number] =
+    len < 1e-9 ? [1, 0, 0] : [dx / len, dy / len, dz / len]
+  return {
+    id,
+    nodeId: pipe.id,
+    position,
+    direction,
+    diameter: pipe.diameter,
+    system: pipe.system,
+  }
+}
+
 function projectToAngleLock(
   from: [number, number, number],
   raw: [number, number, number],
@@ -309,11 +336,14 @@ const PipeSegmentTool = () => {
           ...(cross ? [cross.runUpdate as { id: AnyNode['id']; data: Partial<AnyNode> }] : []),
         ],
       })
+      const nextPipe = pipes.at(-1)
+      const nextStart = nextPipe ? nextPipe.path[nextPipe.path.length - 1]! : end
+      const nextPort = nextPipe ? pipeEndPort(nextPipe, 'end') : endPort
       triggerSFX('sfx:item-place')
-      setDraftStart(null)
+      setDraftStart(nextStart)
       setSnapTarget(null)
-      startPortRef.current = null
-      startBodyRef.current = null
+      startPortRef.current = nextPort
+      startBodyRef.current = nextPort ? null : endBody
       altAnchorRef.current = null
       setAltActive(false)
     }
@@ -483,6 +513,14 @@ const PipeSegmentTool = () => {
         triggerSFX('sfx:grid-snap')
         startPortRef.current = port
         startBodyRef.current = port ? null : body
+        // Continue an existing run at its true size: adopt the snapped
+        // pipe's diameter so the new segment carries on at the same gauge
+        // instead of whatever size the tool last drew.
+        const ownerId = port?.nodeId ?? (port ? null : body?.nodeId)
+        const owner = ownerId ? useScene.getState().nodes[ownerId] : null
+        if (owner?.type === 'pipe-segment' && owner.diameter !== diameterRef.current) {
+          setDiameter(owner.diameter)
+        }
         setDraftStart(point)
         return
       }
@@ -617,7 +655,7 @@ const PipeSegmentTool = () => {
           dimension pill rides just above the cursor. */}
       {cursorPos && (
         <>
-          <CursorSphere position={cursorPos} />
+          <CursorSphere color={snapTarget ? SNAP_CURSOR_COLOR : undefined} position={cursorPos} />
           {pillParts && (
             <group position={cursorPos}>
               <Html