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/get-scene.test.ts

@@ -0,0 +1,51 @@
+import { beforeEach, describe, expect, test } from 'bun:test'
+import { Client } from '@modelcontextprotocol/sdk/client/index.js'
+import { InMemoryTransport } from '@modelcontextprotocol/sdk/inMemory.js'
+import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
+import { SceneBridge } from '../bridge/scene-bridge'
+import { registerGetScene } from './get-scene'
+
+describe('get_scene', () => {
+  let client: Client
+  let bridge: SceneBridge
+
+  beforeEach(async () => {
+    bridge = new SceneBridge()
+    bridge.setScene({}, [])
+    bridge.loadDefault()
+    const server = new McpServer({ name: 'test', version: '0.0.0' })
+    registerGetScene(server, bridge)
+    const [srvT, cliT] = InMemoryTransport.createLinkedPair()
+    client = new Client({ name: 'test-client', version: '0.0.0' })
+    await Promise.all([server.connect(srvT), client.connect(cliT)])
+  })
+
+  test('returns scene with nodes and rootNodeIds', async () => {
+    const result = await client.callTool({ name: 'get_scene', arguments: {} })
+    expect(result.isError).toBeFalsy()
+    const text = (result.content as Array<{ type: string; text: string }>)[0]!.text
+    const parsed = JSON.parse(text)
+    expect(Array.isArray(parsed.rootNodeIds)).toBe(true)
+    expect(parsed.rootNodeIds.length).toBeGreaterThan(0)
+    expect(typeof parsed.nodes).toBe('object')
+    expect(Object.keys(parsed.nodes).length).toBeGreaterThan(0)
+  })
+
+  test('reflects mutations to the bridge', async () => {
+    const beforeCount = Object.keys(bridge.getNodes()).length
+    bridge.setScene({}, [])
+    const result = await client.callTool({ name: 'get_scene', arguments: {} })
+    const parsed = JSON.parse((result.content as Array<{ type: string; text: string }>)[0]!.text)
+    expect(parsed.rootNodeIds.length).toBe(0)
+    expect(Object.keys(parsed.nodes).length).toBe(0)
+    expect(beforeCount).toBeGreaterThan(0)
+  })
+
+  test('returns structured content', async () => {
+    const result = await client.callTool({ name: 'get_scene', arguments: {} })
+    expect(result.structuredContent).toBeDefined()
+    expect(
+      Array.isArray((result.structuredContent as { rootNodeIds: unknown[] }).rootNodeIds),
+    ).toBe(true)
+  })
+})