map: aircraft layer is never added when sync registers before styleReady

Found and verified during the flake campaign (#137, deferred there as out of scope for a flake PR); filing so it survives as its own work item.

`src/ui/shared/map/maplibre/adapter.ts`: line 245 registers `sync` before line 253 sets `styleReady`, so the first `style.load` bails at the line 163 guard and the aircraft layer is never added. `triggerRepaint()` at line 567 then prevents `idle` from ever serving as the retry path.

Two e2e specs assert `data-aircraft-layer` today, which makes the attribute unusable as a readiness gate until this is fixed (context: #209, #210 both had to route around it).

Line numbers are as of the 2026-07-30 audit; re-grep before relying on them.