feat(mcp): implement 19 scene query and mutation tools

Scene querying: get_scene, get_node, describe_node, find_nodes, measure.
Scene mutation (undoable, atomic): apply_patch, create_level, create_wall,
place_item, cut_opening, set_zone, duplicate_level, delete_node.
Undo/redo: undo, redo.
Export: export_json, export_glb (not_implemented stub).
Validation: validate_scene, check_collisions.

Each tool has:
- Exported Zod input + output schemas
- register<Tool>(server, bridge) wiring function
- Bun test with happy-path + error-path coverage via InMemoryTransport

59 tool tests, all passing end-to-end through MCP protocol.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/mcp/src/tools/cut-opening.ts

@@ -0,0 +1,61 @@
+import type { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
+import type { AnyNodeId } from '@pascal-app/core/schema'
+import { DoorNode, WindowNode } from '@pascal-app/core/schema'
+import { z } from 'zod'
+import type { SceneBridge } from '../bridge/scene-bridge'
+import { ErrorCode, throwMcpError } from './errors'
+import { NodeIdSchema } from './schemas'
+
+export const cutOpeningInput = {
+  wallId: NodeIdSchema,
+  type: z.enum(['door', 'window']),
+  position: z.number().min(0).max(1),
+  width: z.number().positive(),
+  height: z.number().positive(),
+}
+
+export const cutOpeningOutput = {
+  openingId: z.string(),
+}
+
+export function registerCutOpening(server: McpServer, bridge: SceneBridge): void {
+  server.registerTool(
+    'cut_opening',
+    {
+      title: 'Cut opening',
+      description:
+        'Cut a door or window opening into an existing wall. position is a parametric 0..1 offset along the wall centreline.',
+      inputSchema: cutOpeningInput,
+      outputSchema: cutOpeningOutput,
+    },
+    async ({ wallId, type, position, width, height }) => {
+      const wall = bridge.getNode(wallId as AnyNodeId)
+      if (!wall) {
+        throwMcpError(ErrorCode.InvalidParams, `Wall not found: ${wallId}`)
+      }
+      if (wall.type !== 'wall') {
+        throwMcpError(ErrorCode.InvalidParams, `Node ${wallId} is a ${wall.type}, expected wall`)
+      }
+
+      // wallT is stored on door/window children via position in the schema;
+      // the core systems look up wallId and derive placement from `position[0]`
+      // being on the wall-local axis. We set wallId explicitly so the runtime
+      // can associate the opening with its parent wall.
+      const base = {
+        wallId,
+        width,
+        height,
+        position: [position, height / 2, 0] as [number, number, number],
+      }
+
+      const opening = type === 'door' ? DoorNode.parse(base) : WindowNode.parse(base)
+      const id = bridge.createNode(opening, wallId as AnyNodeId)
+
+      const payload = { openingId: id as string }
+      return {
+        content: [{ type: 'text' as const, text: JSON.stringify(payload) }],
+        structuredContent: payload,
+      }
+    },
+  )
+}