Vacuum first-use path: materialize the marker, count rectangle rooms, fix the toasts

Audit HP-1540-01 (High): an auto-discovered vacuum has no config marker
until the device dialog is saved once, yet the live-position section was
already interactive. setVac, _vacSaveMatrix and auto-calibration all did
cfg.markers.find(...) and silently bailed out — while the auto-calibration
toast still claimed success. Every vacuum edit now materializes a minimal
marker (same id/binding the dialog Save would produce), _vacSaveMatrix
reports whether the write landed, and success toasts are gated on it.

HP-1540-04: the auto-calibration room matcher accepted only polygon rooms
and told users their room names did not match. It goes through the shared
roomPoly() now, so legacy x/y/w/h rectangles count like everywhere else.

HP-1540-06: the no-rooms/no-match/rough-fit toasts pointed at the removed
point calibration; they now point at the fit panel that shipped instead,
and docs/VACUUM.md Setup UX describes the actual UI. Also extracted
vacMapIdFromAttrs as the explicit frontend half of the map-id contract
(backend half lands with HP-1540-02).

Regressions: demo/smoke_vacuum_firstuse.mjs starts from cfg.markers=[]
(the fixture gap the audit called out) with rectangle plan rooms and a
zero map_index, and fails 11 checks on the v1.54.0 bundle; i18n unit test
asserts no point/точк wording in either language.

src/vacuum.ts

@@ -81,6 +81,19 @@ const num = (v: unknown): number | null => {
   return Number.isFinite(n) ? n : null;
 };
 
+/**
+ * Map-id normalisation contract, shared with the backend recorder
+ * (custom_components/houseplan/trails.py: resolve_map_id). The FIRST value
+ * that is not null/undefined wins — truthiness is wrong here, because a
+ * zero-based `map_index: 0` is a perfectly valid first map and an empty
+ * string is still an id. The backend used an `or`-chain and dropped the
+ * zero, so server trails were stored under a key the renderer never looked
+ * up (HP-1540-02).
+ */
+export function vacMapIdFromAttrs(attrs: Record<string, any>): string {
+  return String(attrs.map_name ?? attrs.current_map ?? attrs.map_index ?? attrs.selected_map ?? 'default');
+}
+
 /**
  * Normalise the attribute zoo. One parser instead of per-brand classes: the
  * three Tier-A integrations (Xiaomi Cloud Map Extractor, Tasshack
@@ -134,7 +147,7 @@ export function readVacTelemetry(attrs: Record<string, any> | null | undefined):
       rooms.push(room);
     }
   }
-  const mapId = String(attrs.map_name ?? attrs.current_map ?? attrs.map_index ?? attrs.selected_map ?? 'default');
+  const mapId = vacMapIdFromAttrs(attrs);
   if (!pos && !rooms.length && !path) return null;
   return { pos, path, rooms, mapId };
 }