feat(05-01): RoutingSource contract + day-one route model + fixture seed schema

- types.ts: the D-01 backend-ladder seam (fixture -> wasm-router -> valhalla),
  D-03 null contract documented on the interface, D-07 day-one fields
  (RouteStep typed + RouteGeometry.cumulativeDistanceM, GUID-05/06 obligation)
- route-fixtures.json: committed EMPTY seed with the ODbL header
  (license/attribution/notice, T-05-06) — plan 05-02 populates it

routing/src/data/route-fixtures.json

@@ -0,0 +1,9 @@
+{
+  "_license": "ODbL-1.0",
+  "_attribution": "© OpenStreetMap contributors",
+  "_notice": "Route geometry © OpenStreetMap contributors, precomputed from the public OSRM demo server (router.project-osrm.org) at build time between fixed public landmark coordinates. ODbL v1.0 — https://opendatacommons.org/licenses/odbl/1-0/",
+  "_source": "OSRM demo server (router.project-osrm.org) — build-time fetch, never a runtime dependency",
+  "version": 1,
+  "originToleranceM": 200,
+  "pairs": []
+}

routing/src/types.ts

@@ -0,0 +1,132 @@
+/*
+ * types.ts — the routing contracts (D-01, D-03, D-05, D-07, D-11).
+ * ----------------------------------------------------------------
+ * RoutePoint / RouteRequest / RouteResult / RoutingSource are the seam
+ * every backend implements: the build-time fixture corpus (backend #1,
+ * "fixture", this phase), the client-side WASM router (backend #2,
+ * "wasm-router" — OSS track, post-v1; origin+destination never touch a
+ * server), and Valhalla-on-VPS (backend #3, documented provision path,
+ * not shipped). The ladder is DOCUMENTED, not switchable: no env read,
+ * no config read, no dynamic backend registry (T-05-04) — the import
+ * site constructs the backend in code (plan 05-04).
+ *
+ * THE NULL CONTRACT IS LOAD-BEARING (D-03): route() resolving to NULL is
+ * the honest "router pending" state — an unknown destination, or an
+ * origin outside the fixture corpus's tolerance. Never a blank map,
+ * never a fake route, never a thrown error for a normal miss.
+ *
+ * No logging, no storage, no network (D-05/D-12/D-15 analog): request
+ * coordinates never leave the caller's frame.
+ */
+
+/** A WGS84 point. */
+export interface RoutePoint {
+  lat: number;
+  lng: number;
+}
+
+/** A routing request. The origin is the live fix (memory only — GEO-03/D-07). */
+export interface RouteRequest {
+  origin: RoutePoint;
+  /** The gazetteer id resolved by the Phase 4 destination resolver. */
+  destinationId: string;
+}
+
+/** Distance/duration summary. Distances in meters, durations in seconds. */
+export interface RouteSummary {
+  distanceM: number;
+  durationS: number;
+}
+
+/**
+ * A maneuver step — DAY-ONE FIELD (D-07, GUID-05/06 upstream obligation).
+ * Fixture-world steps are ALWAYS empty arrays (D-10 defers instructions to
+ * Phase 6): an empty array is honest "not wired"; a fabricated step list
+ * would not be. Real step geometry arrives with backends #2/#3.
+ */
+export interface RouteStep {
+  distanceM?: number;
+  durationS?: number;
+  name?: string;
+  /** polyline6-encoded step geometry (backend #2/#3 populate this). */
+  geometry?: string;
+}
+
+/**
+ * Decoded geometry + the snapped-progress support field — DAY-ONE FIELD
+ * (D-07, GUID-05/06 upstream obligation): Phase 6's guidance walks a live
+ * fix along cumulativeDistanceM instead of re-deriving it per fix.
+ */
+export interface RouteGeometry {
+  points: RoutePoint[];
+  /** Same length as points; [0] === 0; non-decreasing. Meters along the line. */
+  cumulativeDistanceM: number[];
+}
+
+/** One routable alternative. options[0] of a result is the BEST route. */
+export interface RouteOption {
+  geometry: RouteGeometry;
+  summary: RouteSummary;
+  steps: RouteStep[];
+}
+
+export interface RouteResult {
+  destinationId: string;
+  origin: RoutePoint;
+  /** 1..3 options, index 0 = best (order preserved from the backend). */
+  options: RouteOption[];
+  /** === the RoutingSource name that produced it. */
+  backend: string;
+}
+
+/**
+ * The pluggable routing seam (D-01). Backends: "fixture" (this phase) →
+ * "wasm-router" (OSS track, backend #2 — client-side, origin+destination
+ * never touch a server) → "valhalla" (VPS, backend #3). Backends #2/#3 do
+ * NOT ship in this phase — the interface exists so they slot in without a
+ * client rewrite, exactly parallel to SearchSource's ladder (D-03/D-04).
+ *
+ * THE NULL CONTRACT IS LOAD-BEARING (D-03): route() resolving to NULL is
+ * the honest "router pending" state — an unknown destination, or an origin
+ * outside the fixture corpus's tolerance. Never a blank map, never a fake
+ * route, never a thrown error for a normal miss.
+ *
+ * No logging, no storage, no network (D-05/D-12/D-15 analog): request
+ * coordinates never leave the caller's frame.
+ */
+export interface RoutingSource {
+  readonly name: string;
+  route(req: RouteRequest): Promise<RouteResult | null>;
+}
+
+/** One committed fixture route — the polyline6 string stored VERBATIM
+ *  from the build-time OSRM demo response (RESEARCH Finding 1). */
+export interface FixtureRoute {
+  /** polyline6, stored VERBATIM from the OSRM demo response. */
+  geometry: string;
+  distanceM: number;
+  durationS: number;
+}
+
+/** One golden origin→destination pair of the fixture corpus (D-02). */
+export interface FixturePair {
+  /** "<origin-id>-to-<dest-id>", slug charset — also the ?fixpair= knob value. */
+  pairId: string;
+  origin: { lat: number; lng: number; label: string };
+  destinationId: string;
+  /** Best-first, 1..3 entries (OSRM demo returns best-first; preserved). */
+  routes: FixtureRoute[];
+}
+
+/** The committed dataset envelope (route-fixtures.json) — the ODbL
+ *  attribution travels INSIDE the file, the gazetteer's three-surfaces
+ *  pattern (T-05-06). Tests inject synthetic values of this shape. */
+export interface RouteFixturesFile {
+  _license: string;
+  _attribution: string;
+  _notice: string;
+  _source: string;
+  version: number;
+  originToleranceM: number;
+  pairs: FixturePair[];
+}