Fix map typecheck in CI: add peer deps as devDependencies

leaflet, react-leaflet, and @types/leaflet are peer dependencies of
the map package. In CI, pnpm's strict isolation means they aren't
accessible from the package directory during standalone tsc. Adding
them as devDependencies ensures they're installed for typechecking
while consumers still provide them at runtime via peer deps.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/map/package.json

@@ -20,5 +20,10 @@
     "react-dom": ">=18",
     "leaflet": ">=1.9",
     "react-leaflet": ">=5"
+  },
+  "devDependencies": {
+    "@types/leaflet": "^1.9.21",
+    "leaflet": "^1.9.4",
+    "react-leaflet": "^5.0.0"
   }
 }