Add spinning donut screensaver with matrix rain
Terminal screensaver written in C, triggered by tmux lock-after-time
(180s idle), bind S, or `donut` alias. Features:
- Spinning torus with precomputed trig tables, randomized rotation
- Matrix rain overlay — donut luminance colors the rain characters
- 64-shade teal foreground palette with gradual dimming over time
- Chunky 7x5 clock with shadow, blinking colon, periodic drift
- Activity time display below clock (read from heartbeat state file)
- Rim lighting and ambient occlusion on donut edges
- RLE escape state machine — only emits SGR on shade transitions
- Row-skip rendering — empty/leading/trailing regions use cursor jumps
- Projection runs at adaptive rate (24fps bright, 6fps dim)
- select()-based frame pacing, deep sleep after 2hr (1fps)
- Resume detection — flushes stale PTY output after sleep/lock
- Mouse click to quit (SGR + X11 protocols, release filtered)
- write_all() retries partial writes, SIGPIPE handled gracefully
- Alternate screen buffer preserves shell scrollback
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Andrejus
e686b6396d