feat(ui): render the Cockpit instruments, route and vision selector from a store

The Cockpit controller no longer writes the HUD's instruments, the flight
plan card, the visor's destination arrow or the vision selector. It keeps
them as plain state, starting from cockpitInstrumentState.js, and
publishes copies to the gev-cockpit store: the instruments on every HUD
update, the route only when it changed, the vision selector when the mode
changes. CockpitView renders the callsign, aircraft meta and emergency
mark, speed and altitude rims and ticks, compass tape, clock, position,
HUD layer, destination arrow and vision selector; a new CockpitRoute
component renders the flight plan card inside the briefing card.

The odometer readouts become CockpitRollingValue components. Their
throttle and digit roll move unchanged from setCockpitRollingValue into
cockpitRollingValue.js: every accepted reading restamps the throttle, a
change inside it is dropped, and each accepted change draws fresh glyphs
so the roll animation restarts. A rim tick with no reading still hides
where it stood, and a hidden arrow keeps its last angle and label.

In a dev build the HUD's Vue patch costs about 0.5 ms per update (1.4 ms
at 4x CPU throttle), against 0.4 ms (2.1 ms) for the DOM writes it
replaces, at about 10 updates a second.

docs/VUE-MIGRATION.md

@@ -130,12 +130,18 @@ They contain no application state.
    Cockpit (in progress: `CockpitBriefing` renders the briefing card's
    pages, cycle toggle, regional news and local conditions, and
    `CockpitContext` the Contact card's scope, navigation, counts, nearest
-   contact and weather toggle, from the `gev-cockpit` store that the Cockpit
-   controller publishes to, starting from `cockpitBriefPages.js` and
-   `cockpitContextState.js`, which both read; the controls keep the
-   controller's listeners, and the cards' visibility, collapse and layout
-   stay with the controller. The signal rows, the route card, the
-   instruments and the radio controls follow; the signal rows become a
+   contact and weather toggle, `CockpitView` the instruments, destination
+   arrow and vision selector, and `CockpitRoute` the flight plan card, from
+   the `gev-cockpit` store that the Cockpit controller publishes to,
+   starting from `cockpitBriefPages.js`, `cockpitContextState.js` and
+   `cockpitInstrumentState.js`, which both read; the odometer readouts
+   (`CockpitRollingValue`) keep their throttle and roll in
+   `cockpitRollingValue.js`. The instruments publish on every HUD update
+   (about 10 Hz); in a dev build their Vue patch costs about 0.5 ms, close
+   to the DOM writes it replaced. The controls keep the controller's
+   listeners, and the cards' visibility, collapse and layout stay with the
+   controller. The signal rows and the radio controls follow; the signal
+   rows become a
    component that keeps their focus-safe reorder, since a keyed Vue list
    would move the focused row and drop focus several times a second).
    Layers that write into the right rail directly gain a slot instead.