Extract @trails-cool/map-core package from Planner

New renderer-agnostic package with zero dependencies:
- Tile configs (base layers, overlay layers)
- Color palettes (surface, highway, smoothness, tracktype, cycleway,
  bikeroute, elevation, maxspeed) — 8 color maps + 3 color functions
- POI category definitions (9 categories with Overpass queries, icons,
  colors, profile mappings)
- Z-index layering constants
- Snap distance constant

Updated 15 consuming files to import from @trails-cool/map-core.
Deleted poi-categories.ts and z-index.ts from the Planner (fully moved).
packages/map re-exports tile configs from map-core for backwards compat.

All 117 tests pass, no user-facing changes.

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

packages/map/package.json

@@ -7,6 +7,9 @@
   },
   "main": "./src/index.ts",
   "types": "./src/index.ts",
+  "dependencies": {
+    "@trails-cool/map-core": "workspace:*"
+  },
   "peerDependencies": {
     "react": ">=18",
     "react-dom": ">=18",