slab/menubar: per-edge session colors, inline session list, mute toggle
Polygon icon now strokes each edge with its own session's state color
(cyan working / pulsing red awaiting / blinking gray stale) instead of
homogenizing into one aggregate hue, so a hexagon of 3-working/3-paused
threads reads as 3 cyan + 3 throbbing red edges. Dropdown gets the same
treatment: sessions are inlined directly into the main menu (no more
nested submenu) and each row's status dot + label is tinted to match
the icon. Adds a "Mute ambient sonification" checkbox backed by
~/.local/share/slab/state/muted; claude-stop.sh respects it by skipping
chimes/TTS/beeps and force-stopping ambient while the flag is present.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>