First launch with blur blurs and saves to ~/.cache/moonset/. Subsequent
starts load the cached PNG directly (~9x faster). Cache invalidates
when wallpaper path, size, mtime, or sigma changes.
Feature-parity with Python v0.2.0. Same CSS, same UI, same actions.
Single 3.1 MB binary with embedded resources (CSS, wallpaper, avatar).
Modules: power.rs, i18n.rs, config.rs, users.rs, panel.rs, main.rs
45 unit tests passing. Python sources retained as reference.