Split ElevationChart + PlannerMap into deep modules; add visual regression testing

ElevationChart (1013 lines) split into:
- elevation-chart-draw.ts — pure drawElevationChart(ctx, w, h, params) function
- use-elevation-data.ts — useElevationData(routeData) hook
- ElevationChart.tsx — ~300 lines, interaction + render only

PlannerMap (869 lines) split into:
- MapHelpers.tsx — 7 Leaflet sub-components (MapExposer, RouteFitter, MapClickHandler,
  CursorTracker, NoGoAreaButton, OverlaySync, PoiRefresher)
- use-waypoint-manager.ts — all waypoint CRUD + route data sync
- use-gpx-drop.ts — GPX drag-and-drop hook
- PlannerMap.tsx — ~200 lines, orchestration only

Add Vitest browser visual regression tests for drawElevationChart via
@vitest/browser + Playwright (toMatchScreenshot). Tests cover plain, grade,
elevation, surface color modes plus hover and drag-select states.

Add update-visual-snapshots.yml workflow: triggered by workflow_dispatch or
the `update-snapshots` PR label; commits snapshots back to the branch.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/planner/package.json

@@ -9,7 +9,9 @@
     "start": "node server.ts",
     "typecheck": "react-router typegen && tsc",
     "lint": "eslint .",
-    "test": "vitest run"
+    "test": "vitest run",
+    "test:visual": "vitest run --config vitest.browser.config.ts",
+    "test:visual:update": "vitest run --config vitest.browser.config.ts --update-snapshots"
   },
   "dependencies": {
     "@codemirror/commands": "^6.10.3",
@@ -22,9 +24,9 @@
     "@sentry/node": "catalog:",
     "@sentry/react": "catalog:",
     "@trails-cool/db": "workspace:*",
-    "@trails-cool/jobs": "workspace:*",
     "@trails-cool/gpx": "workspace:*",
     "@trails-cool/i18n": "workspace:*",
+    "@trails-cool/jobs": "workspace:*",
     "@trails-cool/map": "workspace:*",
     "@trails-cool/map-core": "workspace:*",
     "@trails-cool/sentry-config": "workspace:*",
@@ -52,6 +54,7 @@
     "@types/react": "catalog:",
     "@types/react-dom": "catalog:",
     "@types/ws": "^8.18.1",
+    "@vitest/browser": "^4.1.5",
     "leaflet.markercluster": "^1.5.3",
     "pino-pretty": "^13.1.3",
     "tailwindcss": "catalog:",