docs: add macOS VM (Lume) platform guide

Add documentation for running Clawdbot in a sandboxed macOS VM
using Lume. This provides an alternative to buying dedicated
hardware or using cloud instances.

The guide covers:
- Installing Lume on Apple Silicon Macs
- Creating and configuring a macOS VM
- Installing Clawdbot inside the VM
- Running headlessly for 24/7 operation
- iMessage integration via BlueBubbles
- Saving golden images for easy reset

docs/docs.json

@@ -1048,6 +1048,7 @@
         "pages": [
           "platforms",
           "platforms/macos",
+          "platforms/macos-vm",
           "platforms/ios",
           "platforms/android",
           "platforms/windows",