filtering: hiding is an explicit per-device flag (docs/FILTERING.md)

Agreed with the owner: whether a device is on the plan is a CHECKBOX
('Hide device from plan', every kind incl. virtual), not a runtime
algorithm. The old filter survives only as the SEEDER of those flags.

- marker.hidden is the flag; hidden devices are BUILT (room LQI counts
  them — owner's decision) but rendered only in the device editor with
  'Show hidden' on, ghosted. They cast no glow and no light fill: an
  invisible device casts no visible light (owner's decision).
- seedHiddenBindings(): non-physical devices (excluded domains, Group,
  scene, bridge, myheat children, grouped lamps) in bound areas WITHOUT a
  marker. The editing client materialises them into hidden:true stub
  markers, sets settings.filter_seeded, retires settings.show_all, and
  strips fresh-hidden ids from the red-dot list. Unticking the checkbox
  keeps a hidden:false marker — the seeder never revisits a marked device,
  so the user's decision is final. New non-physical devices hide silently;
  physical ones keep the red-dot flow.
- legacy configs (no filter_seeded) keep the OLD behaviour verbatim —
  runtime filter, shared show_all, hidden-means-gone — until an editing
  client materialises them, so a read-only tablet never sees a half-state.
- 'Show all' is renamed 'Show hidden' and is LOCAL to the tab; the shared
  settings.show_all retires with the runtime filter.
- 'Remove from plan' disappears for auto/entity devices (the checkbox is
  the way); a virtual device's Delete remains a real deletion.
- docs/FILTERING.md is the source of truth for the mechanism.

Tests: seeder/seeded/legacy/lights units (146), smoke_hidden_flag with 12
assertions (68 smokes). Inventory: 146 / 51 / 43 / 68.

src/space-render.ts

@@ -65,7 +65,8 @@ export function renderSpaceStatic(o: StaticRenderOpts): TemplateResult | null {
     loc,
     iconRules,
   });
-  const devs = all.filter((d) => d.space === o.spaceId);
+  // the static card never shows hidden devices — there is no editor here
+  const devs = all.filter((d) => d.space === o.spaceId && !d.hidden);
   const defPos = defaultPositions(devs, space, iconPct);
 
   const roomShapes = space.rooms