luban sync

Re-read vcpkg.json + luban.toml in the current project, regenerate luban.cmake.

luban sync

When you'd use it

• Just pulled a project from git, want to make sure luban.cmake is up to date with the in-tree vcpkg.json
• Hand-edited vcpkg.json (e.g., to add "features" or "overrides" that luban add doesn't expose)
• Changed luban.toml [scaffold] warnings = "strict" and want it reflected
• luban.cmake got accidentally deleted

What it changes

Only luban.cmake. vcpkg.json and luban.toml are read-only inputs.