feat(ui): render the Weather readout as one component

createWeatherPanel() computes the readout it shows (forecast and event
cards, the observed group's scope, the history timeline state and observed
cards) and renders WeatherReadout synchronously into the panel body, so a
newly opened card is still revealed after measuring. The hand-built hosts
and the separate card and timeline builders are gone; markup, open-card
choice, first appearance and teardown are unchanged.

docs/VUE-MIGRATION.md

@@ -81,7 +81,8 @@ They contain no application state.
    the rail cards, card blocks and timeline (`src/ui/rail/`) render through
    Vue's synchronous `render()` behind `createRailCards()`,
    `createRailCardBlocks()` and `createRailTimeline()`. Order: Scenes (done: `SceneOptions` and
-   `SceneShotList` over the `gev-scenes` store), Weather, Recent imagery,
+   `SceneShotList` over the `gev-scenes` store), Weather (done: the owner
+   renders `WeatherReadout` from the view it computes), Recent imagery,
    Street level, CCTV, Layers, Display, Context and Radio, the command dock,
    the phone shell, then Cockpit. Layers that write into the right rail
    directly gain a slot instead.