hidden devices: blue ghosts, no live-state paint

A hidden device and an unavailable one both rendered as translucent dark —
indistinguishable at a glance, and a lit hidden lamp still glowed yellow
through the ghost (owner's report). A ghost is CONFIGURATION, not status:

- blue dashed ghost (accent-tinted, color-mix with an rgba fallback for old
  WebViews), clearly apart from the grey 'unavailable' icon;
- no state classes, no RGB tint, no alarm pulse, no active ripple on hidden
  devices — the only thing a ghost says is 'I am hidden, click to unhide'.

smoke_hidden_flag grew two assertions: the ghost carries no state classes
and is blue/dashed.

demo/smoke_hidden_flag.mjs

@@ -39,6 +39,13 @@ Object.assign(out, await page.evaluate(async () => {
   o.noGhostsInView = !sr().querySelector('.dev.ghost');
   c._setMode('devices'); c.requestUpdate(); await c.updateComplete;
   o.ghostInEditor = !!sr().querySelector('.dev.ghost');
+  // призрак — конфигурация, не статус: ни жёлтого, ни unavail, ни тревоги
+  const g = sr().querySelector('.dev.ghost');
+  o.ghostHasNoState = !!g && !g.classList.contains('on') && !g.classList.contains('open')
+    && !g.classList.contains('unavail') && !g.classList.contains('alarm');
+  // и он синий, а не тёмный — отличим от недоступного устройства
+  o.ghostIsBlue = !!g && getComputedStyle(g).borderStyle.includes('dashed')
+    && getComputedStyle(g).borderColor !== 'rgb(255, 255, 255)';
   // тумблер локальный: конфиг не трогается
   o.toggleIsLocal = c._serverCfg.settings.show_all === undefined;