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>

apps/planner/app/components/PlannerMap.tsx

@@ -13,7 +13,7 @@ import { usePois } from "~/lib/use-pois";
 import { useProfileDefaults } from "~/lib/use-profile-defaults";
 import { useYjsPoiSync } from "~/lib/use-yjs-poi-sync";
 import { snapToPoi } from "~/lib/poi-snap";
-import { Z_CURSOR, Z_WAYPOINT, Z_WAYPOINT_HIGHLIGHTED, Z_HIGHLIGHT } from "~/lib/z-index";
+import { Z_CURSOR, Z_WAYPOINT, Z_WAYPOINT_HIGHLIGHTED, Z_HIGHLIGHT } from "@trails-cool/map-core";
 import { NoGoAreaLayer } from "./NoGoAreaLayer";
 import { ColoredRoute, findSegmentForPoint, type ColorMode } from "./ColoredRoute";
 import { RouteInteraction } from "./RouteInteraction";