feat: task 2.1 MapView singleton + mapReady gate

- pnpm add maplibre-gl + -D @types/geojson.
- src/map/core/styles.ts: defaultStyle (OSM raster bootstrap; 2.2
  replaces with the basemap-switcher descriptor table).
- src/map/core/map-view.tsx: module-level Map singleton lazily created
  on first <MapView> mount, attached to a class="trm-map-host" detached
  <div> that React refs append/remove on mount/unmount. Style-data
  lifecycle flips mapReady false on every styledata event, polls
  loaded() at 33ms intervals, flips ready true once the style is
  loaded — the canonical MapLibre style-swap dance.
- Exports getMap()/getMapReady()/subscribeMapReady()/useMapReady (via
  useSyncExternalStore for SSR-safe + concurrent-safe reads). getMap()
  throws if called pre-mount; the explicit failure mode beats a
  null-able top-level export.
- src/routes/_authed/monitor.tsx: new /monitor route, full-viewport
  <MapView /> for 2.1 (no children — subsequent tasks plug in here).
- src/routes/_authed/index.tsx: home-page card now links to /monitor.
- eslint.config.js: override for src/map/** + src/live/** disables
  react-refresh/only-export-components. Same pattern as the existing
  overrides for shadcn primitives and route files.

Deviation: spec sketched a top-level `map` constant export; implemented
as `getMap(): MapLibreMap` (a function) so the singleton stays lazy
until <MapView> mounts. Top-level constant would either force eager
init (breaks SSR/tests) or be nullable (footgun). The function form
throws a clear error if called pre-mount.

Bundle: /monitor lazy chunk is 1MB raw / 274KB gzipped (MapLibre + CSS).
Other routes unaffected. Vite chunk-size warning is harmless.

.planning/phase-2-live-map/README.md

@@ -46,17 +46,17 @@ When Phase 2 is done:
 
 ## Tasks
 
-| #   | Task                                                                                                  | Status |
-| --- | ----------------------------------------------------------------------------------------------------- | ------ |
-| 2.1 | [MapView singleton + mapReady gate](./01-mapview-singleton.md)                                        | ⬜     |
-| 2.2 | [Tile-source switcher](./02-tile-source-switcher.md)                                                  | ⬜     |
-| 2.3 | [Sprite preload (racing categories)](./03-sprite-preload.md)                                          | ⬜     |
-| 2.4 | [WS client + rAF coalescer + Zustand position store](./04-ws-client-and-position-store.md)            | ⬜     |
-| 2.5 | [MapPositions (clustered + selected sources)](./05-map-positions.md)                                  | ⬜     |
-| 2.6 | [MapTrails (bounded ring buffer, polyline rendering)](./06-map-trails.md)                             | ⬜     |
-| 2.7 | [Event picker (subscription driver)](./07-event-picker.md)                                            | ⬜     |
-| 2.8 | [Camera control trio](./08-camera-trio.md)                                                            | ⬜     |
-| 2.9 | [Connection status + per-device last-seen indicators](./09-connection-status.md)                      | ⬜     |
+| #   | Task                                                                                       | Status |
+| --- | ------------------------------------------------------------------------------------------ | ------ |
+| 2.1 | [MapView singleton + mapReady gate](./01-mapview-singleton.md)                             | 🟩     |
+| 2.2 | [Tile-source switcher](./02-tile-source-switcher.md)                                       | ⬜     |
+| 2.3 | [Sprite preload (racing categories)](./03-sprite-preload.md)                               | ⬜     |
+| 2.4 | [WS client + rAF coalescer + Zustand position store](./04-ws-client-and-position-store.md) | ⬜     |
+| 2.5 | [MapPositions (clustered + selected sources)](./05-map-positions.md)                       | ⬜     |
+| 2.6 | [MapTrails (bounded ring buffer, polyline rendering)](./06-map-trails.md)                  | ⬜     |
+| 2.7 | [Event picker (subscription driver)](./07-event-picker.md)                                 | ⬜     |
+| 2.8 | [Camera control trio](./08-camera-trio.md)                                                 | ⬜     |
+| 2.9 | [Connection status + per-device last-seen indicators](./09-connection-status.md)           | ⬜     |
 
 ## Files modified
 
@@ -95,9 +95,9 @@ spa/
 ## Tech stack additions
 
 - **`maplibre-gl`** — the rendering engine. Imported directly (no `react-map-gl` wrapper — see [[maps-architecture]] for why).
-- **`maplibre-google-maps`** *(optional, runtime-config-gated)* — protocol adapter for Google's Map Tiles API. Loaded only if `googleMapsKey` is present in the runtime config.
+- **`maplibre-google-maps`** _(optional, runtime-config-gated)_ — protocol adapter for Google's Map Tiles API. Loaded only if `googleMapsKey` is present in the runtime config.
 - **`@types/geojson`** — devDep for typing `Feature` / `FeatureCollection`.
-- **`pmtiles`** *(optional, defer)* — for offline tile archives in remote terrain. Out of scope for v1 of Phase 2.
+- **`pmtiles`** _(optional, defer)_ — for offline tile archives in remote terrain. Out of scope for v1 of Phase 2.
 
 No new test infra (Vitest is Phase 3.6).