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/01-mapview-singleton.md

@@ -190,4 +190,30 @@ For 2.1, no children — the map renders the basemap and nothing else. Subsequen
 
 ## Done
 
-(Filled in when the task lands.)
+Three new files + small updates to existing surfaces:
+
+- **`src/map/core/styles.ts`** — `defaultStyle` exporting an OSM raster `StyleSpecification` (single raster source + raster layer + glyphs URL for label rendering on future symbol layers). 2.2 will replace this with the descriptor table + switcher.
+- **`src/map/core/map-view.tsx`** — singleton + `<MapView>` + `mapReady` gate. Exports `getMap()` (throws if called pre-mount), `getMapReady()`, `subscribeMapReady()`, `useMapReady()` (via `useSyncExternalStore`). The singleton's container has class `trm-map-host` for CSS targeting if global resets ever bite. Style-data lifecycle handler (`onStyleData`) flips ready false → polls `loaded()` → flips ready true; that's the canonical MapLibre style-swap dance.
+- **`src/routes/_authed/monitor.tsx`** — new route at `/monitor` rendering `<MapView />` full-viewport. No children for 2.1; subsequent tasks plug components in here.
+- **`src/routes/_authed/index.tsx`** — home-page card now renders a `<Link to="/monitor">Open live map →</Link>`.
+- **`eslint.config.js`** — added override for `src/map/**` and `src/live/**` disabling `react-refresh/only-export-components`. These modules intentionally co-export non-component utilities (singletons, factories, hooks) alongside the React component. Same pattern as the existing override for `src/ui/primitives/**` and `src/routes/**`.
+
+**Deps installed:** `maplibre-gl@5.24.0` (runtime), `@types/geojson@7946.0.16` (devDep).
+
+**Deviation flagged:**
+
+The spec sketched the singleton's accessor as `map` (a top-level export). Implemented as `getMap(): MapLibreMap` instead — a function call rather than an exported constant. Two reasons:
+1. The singleton is created lazily on first `<MapView>` mount, not at module import. A top-level `map` export would either force eager initialisation (breaks SSR / tests) or be `null` until something mounts (footgun).
+2. `getMap()` throws a clear error if called before `<MapView>` mounts — a missing pre-condition that's easy to surface and easy to read in stack traces. A `null`-able export forces every consumer to add their own null check.
+
+Side-effect-only `Map*` components (2.5+) call `getMap()` from inside their `useEffect` *after* `useMapReady()` returns true, by which point the singleton exists and the style is loaded.
+
+**Smoke check (local `pnpm dev`):**
+- `/monitor` renders a full-viewport OSM map.
+- Pan / zoom / scroll-zoom all work.
+- `/monitor` → `/` → `/monitor` keeps the map responsive (singleton survives navigation).
+- Browser console: `(await import('@/map/core/map-view')).getMapReady()` returns `true` after the page settles.
+
+**Bundle impact:** the `monitor` route is a new lazy chunk (~1MB raw / 274KB gzipped — MapLibre + its CSS). It's loaded only when the route is visited; all other routes are unaffected. Vite emits a chunk-size warning >500KB; expected and harmless. The home page's bundle is unchanged.
+
+Landed in `PENDING_SHA`.