Solves the 'lost window' problem — if the widget gets dragged off-screen
or hidden behind other apps, users can recover it via the tray.
Enables tauri 'tray-icon' feature; tray runs entirely Rust-side so no
new JS capabilities needed.
The widget now spawns 'claude' via portable-pty, sends /usage, parses the
three rendered bars (Current session / Current week all / Current week
Sonnet), and shows the real percentages in the ring + weekly bars. A
background task refreshes every 5 minutes; the title-bar refresh button
forces an immediate fetch.
Drops the cap-tuning UI and tier card from Settings; adds a 'claude command'
override (e.g. 'wsl.exe -- claude' for Windows-host widgets reading WSL
credentials) and a refresh-interval setting. Fixes title-bar buttons getting
swallowed as drag attempts via data-tauri-drag-region="false".
