route-surface-breakdown (Phase 1): Planner-path surface/waytype bars

Synchronous path + rendering for the surface/waytype breakdown:
- map-core `computeSurfaceBreakdown(coords, surfaces, highways)` → distance-
  weighted metres per surface + waytype category (unit-tested);
- `SurfaceBreakdownSchema` in @trails-cool/api;
- nullable `surfaceBreakdown` jsonb on routes + activities;
- Planner `SaveToJournalButton` computes it from the BRouter waytags already in
  routeData and sends it; `api.save-to-journal` forwards it; the journal route
  callback validates + persists (journal is the authoritative validator);
- `SurfaceBreakdown` component (stacked bars per dimension, map-core palettes,
  legend category · % · km largest-first, unknown → "other", hidden when empty)
  on route + activity detail; journal gains a @trails-cool/map-core dep;
- i18n journal.surface.* (en + de).

Phase 2 (async Overpass backfill + SSE for imports/uploads, and the e2e that
seeds a breakdown) follows in a separate PR.

Tests: computeSurfaceBreakdown unit (map-core 36); SurfaceBreakdown component
(jsdom, journal 326). typecheck + lint green; verified in the browser.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/api/src/index.ts

@@ -42,6 +42,9 @@ export {
   type ComputeRouteRequest,
 } from "./routes.ts";
 
+// Surface / waytype breakdown
+export { SurfaceBreakdownSchema, type SurfaceBreakdown } from "./surface-breakdown.ts";
+
 // Activities
 export {
   ActivitySummarySchema, ActivityDetailSchema,

packages/api/src/surface-breakdown.ts

@@ -0,0 +1,15 @@
+import { z } from "zod";
+
+/**
+ * Distance-weighted surface/waytype breakdown (metres per category). Shared
+ * wire shape for the planner→journal handoff and the route/activity read APIs.
+ * Mirrors `SurfaceBreakdown` in `@trails-cool/map-core`.
+ */
+const MetresByCategory = z.record(z.string(), z.number().min(0));
+
+export const SurfaceBreakdownSchema = z.object({
+  surface: MetresByCategory,
+  highway: MetresByCategory,
+});
+
+export type SurfaceBreakdown = z.infer<typeof SurfaceBreakdownSchema>;