Add empty test level and Unreal MCP tooling

- L_TestFlight: empty, zero-gravity level for Phase 0 flight testing,
  set as editor/game default map.
- Enable UnrealMCPython + Python Editor Script Plugin, third-party
  MCP plugin (GenOrca/unreal-mcp v2.2.0) giving direct editor control
  (actors, blueprints, levels, materials, etc.) alongside Epic's
  built-in Unreal MCP plugin.
- Vendor the mcp-server Python source used to bridge to the plugin.
- .mcp.json intentionally gitignored (machine-specific absolute paths).

.gitignore

@@ -24,6 +24,13 @@ Saved/
 Plugins/*/Binaries/
 Plugins/*/Intermediate/
 
+# Python bytecode caches (e.g. plugin-bundled Python tools)
+__pycache__/
+*.pyc
+
 # OS
 .DS_Store
 Thumbs.db
+
+# Machine-specific MCP client config (absolute local paths)
+.mcp.json