The double click was the appindicator extension's, not ours: it reserves
double-click for SNI Activate (instant menu) and delays single-click by
400 ms, so a single click feels dead. Nothing to fix tray-side; documented
in the changelog.

- BRIDGE_QSS restyles the Qt-drawn popup on dark desktops: tonal surfaces,
  hairline borders, hover pill, magenta on the engaged radio; circles for
  radio groups, squares for boolean toggles. Contrast measured: body 14.7:1,
  disabled 6.4:1, radio ring 3.3:1 (bumped from 2.3:1 in review).
- stat rows and the thermal tooltip read in tabular digits.
- every user-visible string loses its em dash (colons, parens, middots);
  same pass on gearbox.py labels (shared with the web Bridge) and the
  launcher blurbs; unknown gearbox placeholder is now n/a, not a bare dash.
- mnemonics on the action rows (&Open Bridge, &GIG UP, &Restart SuperDirt,
  R&ig, &Start at login, Cut G&PU, &Quit); verified over DBusMenu that Qt
  exports them as underscores, so the shell-drawn twin gets them too.
  Literal ampersand does not survive the export, so the copy avoids it.