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.

package.json

@@ -22,6 +22,7 @@
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "lucide-react": "^1.14.0",
+    "maplibre-gl": "^5.24.0",
     "radix-ui": "^1.4.3",
     "react": "^19.2.5",
     "react-dom": "^19.2.5",
@@ -37,6 +38,7 @@
     "@tanstack/react-router-devtools": "^1.166.13",
     "@tanstack/router-cli": "^1.166.40",
     "@tanstack/router-plugin": "^1.167.32",
+    "@types/geojson": "^7946.0.16",
     "@types/node": "^24.12.2",
     "@types/react": "^19.2.14",
     "@types/react-dom": "^19.2.3",