feat: Implement CRDT-based layout system for Vue nodes (#4959)

* feat: Implement CRDT-based layout system for Vue nodes

Major refactor to solve snap-back issues and create single source of truth for node positions:

- Add Yjs-based CRDT layout store for conflict-free position management
- Implement layout mutations service with clean API
- Create Vue composables for layout access and node dragging
- Add one-way sync from layout store to LiteGraph
- Disable LiteGraph dragging when Vue nodes mode is enabled
- Add z-index management with bring-to-front on node interaction
- Add comprehensive TypeScript types for layout system
- Include unit tests for layout store operations
- Update documentation to reflect CRDT architecture

This provides a solid foundation for both single-user performance and future real-time collaboration features.

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

* style: Apply linter fixes to layout system

* fix: Remove unnecessary README files and revert services README

- Remove unnecessary types/README.md file
- Revert unrelated changes to services/README.md
- Keep only relevant documentation for the layout system implementation

These were issues identified during PR review that needed to be addressed.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* refactor: Clean up layout store and implement proper CRDT operations

- Created dedicated layoutOperations.ts with production-grade CRDT interfaces
- Integrated existing QuadTree spatial index instead of simple cache
- Split composables into separate files (useLayout, useNodeLayout, useLayoutSync)
- Cleaned up operation handlers using specific types instead of Extract
- Added proper operation interfaces with type guards and extensibility
- Updated all type references to use new operation structure

The layout store now properly uses the existing QuadTree infrastructure for
efficient spatial queries and follows CRDT best practices with well-defined
operation interfaces.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* refactor: Extract services and split composables for better organization

- Created SpatialIndexManager to handle QuadTree operations separately
- Added LayoutAdapter interface for CRDT abstraction (Yjs, mock implementations)
- Split GraphNodeManager into focused composables:
  - useNodeWidgets: Widget state and callback management
  - useNodeChangeDetection: RAF-based geometry change detection
  - useNodeState: Node visibility and reactive state management
- Extracted constants for magic numbers and configuration values
- Updated layout store to use SpatialIndexManager and constants

This improves code organization, testability, and makes it easier to swap
CRDT implementations or mock services for testing.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* Add node slots to layout tree

* Revert "Add node slots to layout tree"

This reverts commit 460493a620.

* Remove slots from layoutTypes

* Totally not scuffed renderer and adapter

* Revert "Totally not scuffed renderer and adapter"

This reverts commit 2b9d83efb8.

* Revert "Remove slots from layoutTypes"

This reverts commit 18f78ff786.

* Reapply "Add node slots to layout tree"

This reverts commit 236fecb549.

* Revert "Add node slots to layout tree"

This reverts commit 460493a620.

* docs: Replace architecture docs with comprehensive ADR

- Add ADR-0002 for CRDT-based layout system decision
- Follow established ADR template with persuasive reasoning
- Include performance benefits, collaboration readiness, and architectural advantages
- Update ADR index

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Benjamin Lu <benjaminlu1107@gmail.com>

src/composables/graph/useNodeChangeDetection.ts

@@ -0,0 +1,180 @@
+/**
+ * Node Change Detection
+ *
+ * RAF-based change detection for node positions and sizes.
+ * Syncs LiteGraph changes to the layout system.
+ */
+import { reactive } from 'vue'
+
+import type { LGraph, LGraphNode } from '@/lib/litegraph/src/litegraph'
+import { layoutMutations } from '@/services/layoutMutations'
+
+export interface ChangeDetectionMetrics {
+  updateTime: number
+  positionUpdates: number
+  sizeUpdates: number
+  rafUpdateCount: number
+}
+
+/**
+ * Change detection for node geometry
+ */
+export function useNodeChangeDetection(graph: LGraph) {
+  const metrics = reactive<ChangeDetectionMetrics>({
+    updateTime: 0,
+    positionUpdates: 0,
+    sizeUpdates: 0,
+    rafUpdateCount: 0
+  })
+
+  // Track last known positions/sizes
+  const lastSnapshot = new Map<
+    string,
+    { pos: [number, number]; size: [number, number] }
+  >()
+
+  /**
+   * Detects position changes for a single node
+   */
+  const detectPositionChanges = (
+    node: LGraphNode,
+    nodePositions: Map<string, { x: number; y: number }>
+  ): boolean => {
+    const id = String(node.id)
+    const currentPos = nodePositions.get(id)
+
+    if (
+      !currentPos ||
+      currentPos.x !== node.pos[0] ||
+      currentPos.y !== node.pos[1]
+    ) {
+      nodePositions.set(id, { x: node.pos[0], y: node.pos[1] })
+
+      // Push position change to layout store
+      void layoutMutations.moveNode(id, { x: node.pos[0], y: node.pos[1] })
+
+      return true
+    }
+    return false
+  }
+
+  /**
+   * Detects size changes for a single node
+   */
+  const detectSizeChanges = (
+    node: LGraphNode,
+    nodeSizes: Map<string, { width: number; height: number }>
+  ): boolean => {
+    const id = String(node.id)
+    const currentSize = nodeSizes.get(id)
+
+    if (
+      !currentSize ||
+      currentSize.width !== node.size[0] ||
+      currentSize.height !== node.size[1]
+    ) {
+      nodeSizes.set(id, { width: node.size[0], height: node.size[1] })
+
+      // Push size change to layout store
+      void layoutMutations.resizeNode(id, {
+        width: node.size[0],
+        height: node.size[1]
+      })
+
+      return true
+    }
+    return false
+  }
+
+  /**
+   * Main RAF change detection function
+   */
+  const detectChanges = (
+    nodePositions: Map<string, { x: number; y: number }>,
+    nodeSizes: Map<string, { width: number; height: number }>,
+    onSpatialChange?: (node: LGraphNode, id: string) => void
+  ) => {
+    const startTime = performance.now()
+
+    if (!graph?._nodes) return
+
+    let positionUpdates = 0
+    let sizeUpdates = 0
+
+    // Set source for all canvas-driven updates
+    layoutMutations.setSource('canvas')
+
+    // Process each node for changes
+    for (const node of graph._nodes) {
+      const id = String(node.id)
+
+      const posChanged = detectPositionChanges(node, nodePositions)
+      const sizeChanged = detectSizeChanges(node, nodeSizes)
+
+      if (posChanged) positionUpdates++
+      if (sizeChanged) sizeUpdates++
+
+      // Notify spatial change if needed
+      if ((posChanged || sizeChanged) && onSpatialChange) {
+        onSpatialChange(node, id)
+      }
+    }
+
+    // Update metrics
+    const endTime = performance.now()
+    metrics.updateTime = endTime - startTime
+    metrics.positionUpdates = positionUpdates
+    metrics.sizeUpdates = sizeUpdates
+
+    if (positionUpdates > 0 || sizeUpdates > 0) {
+      metrics.rafUpdateCount++
+    }
+  }
+
+  /**
+   * Take a snapshot of current node positions/sizes
+   */
+  const takeSnapshot = () => {
+    if (!graph?._nodes) return
+
+    lastSnapshot.clear()
+    for (const node of graph._nodes) {
+      lastSnapshot.set(String(node.id), {
+        pos: [node.pos[0], node.pos[1]],
+        size: [node.size[0], node.size[1]]
+      })
+    }
+  }
+
+  /**
+   * Check if any nodes have changed since last snapshot
+   */
+  const hasChangedSinceSnapshot = (): boolean => {
+    if (!graph?._nodes) return false
+
+    for (const node of graph._nodes) {
+      const id = String(node.id)
+      const last = lastSnapshot.get(id)
+      if (!last) continue
+
+      if (
+        last.pos[0] !== node.pos[0] ||
+        last.pos[1] !== node.pos[1] ||
+        last.size[0] !== node.size[0] ||
+        last.size[1] !== node.size[1]
+      ) {
+        return true
+      }
+    }
+    return false
+  }
+
+  return {
+    metrics,
+    detectChanges,
+    detectPositionChanges,
+    detectSizeChanges,
+    takeSnapshot,
+    hasChangedSinceSnapshot
+  }
+}