test: add Playwright tests G1-G5 for buildJourneySegments algorithm

Tests load italy-2025 map page to get MapUtils in scope, then exercise the
GPX proximity algorithm with synthetic data via page.evaluate.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WPJztrVGbwic2xTG7G9fjM

tests/ui/gpx-journey.spec.js

@@ -0,0 +1,90 @@
+// @ts-check
+// Tests: G1–G4 — buildJourneySegments algorithm correctness
+// These tests load the italy-2025 map page (which has GPX) to get MapUtils in scope,
+// then call the functions with synthetic data via page.evaluate.
+// Requires demo data: run `make demo-load` before this suite.
+const { test, expect } = require('@playwright/test');
+
+async function getMapUtils(page) {
+    await page.goto('/trips/italy-2025/map');
+    await expect(page.locator('canvas.maplibregl-canvas')).toBeVisible({ timeout: 10000 });
+}
+
+// G1: No GPX → all pairs connected in one segment
+test('G1: all markers connected when no GPX files present', async ({ page }) => {
+    await getMapUtils(page);
+
+    var count = await page.evaluate(function () {
+        var entries = [
+            { lat: '43.0', lng: '11.0', force_connect: false },
+            { lat: '44.0', lng: '12.0', force_connect: false },
+            { lat: '45.0', lng: '13.0', force_connect: false }
+        ];
+        return MapUtils.buildJourneySegments(entries, [], 10).length;
+    });
+
+    expect(count).toBe(1);
+});
+
+// G2: Same GPX file covers both markers → connector suppressed (0 segments)
+test('G2: connector suppressed when same GPX file covers both markers', async ({ page }) => {
+    await getMapUtils(page);
+
+    var count = await page.evaluate(function () {
+        var e1 = { lat: '43.000', lng: '11.000', force_connect: false };
+        var e2 = { lat: '43.010', lng: '11.010', force_connect: false };
+        // Trackpoints covering both (stored as [lat, lng])
+        var track = [[43.000, 11.000], [43.005, 11.005], [43.010, 11.010]];
+        return MapUtils.buildJourneySegments([e1, e2], [track], 10).length;
+    });
+
+    expect(count).toBe(0);
+});
+
+// G3: force_connect overrides GPX suppression
+test('G3: force_connect keeps connector even when GPX covers both markers', async ({ page }) => {
+    await getMapUtils(page);
+
+    var count = await page.evaluate(function () {
+        var e1 = { lat: '43.000', lng: '11.000', force_connect: false };
+        var e2 = { lat: '43.010', lng: '11.010', force_connect: true };
+        var track = [[43.000, 11.000], [43.005, 11.005], [43.010, 11.010]];
+        return MapUtils.buildJourneySegments([e1, e2], [track], 10).length;
+    });
+
+    expect(count).toBe(1);
+});
+
+// G4: Markers near DIFFERENT GPX files → connector kept
+test('G4: connector kept when markers are near different GPX files', async ({ page }) => {
+    await getMapUtils(page);
+
+    var count = await page.evaluate(function () {
+        var e1 = { lat: '43.000', lng: '11.000', force_connect: false };
+        var e2 = { lat: '45.000', lng: '13.000', force_connect: false };
+        // Two separate files — each only covers one marker
+        var trackA = [[43.000, 11.000], [43.005, 11.005]]; // near e1 only
+        var trackB = [[45.000, 13.000], [45.005, 13.005]]; // near e2 only
+        return MapUtils.buildJourneySegments([e1, e2], [trackA, trackB], 10).length;
+    });
+
+    expect(count).toBe(1);
+});
+
+// G5: First pair suppressed, second pair kept → one segment [e2, e3]
+test('G5: suppressed first pair leaves one segment from e2 to e3', async ({ page }) => {
+    await getMapUtils(page);
+
+    var count = await page.evaluate(function () {
+        // e1→e2: covered by track → suppressed; e1 is orphaned (< 2 pts, not pushed)
+        // e2→e3: not covered → connector kept → segment [e2, e3]
+        var e1 = { lat: '43.000', lng: '11.000', force_connect: false };
+        var e2 = { lat: '43.010', lng: '11.010', force_connect: false };
+        var e3 = { lat: '45.000', lng: '13.000', force_connect: false };
+        var track = [[43.000, 11.000], [43.005, 11.005], [43.010, 11.010]]; // covers e1 and e2 only
+        var segs = MapUtils.buildJourneySegments([e1, e2, e3], [track], 10);
+        return segs.length;
+    });
+
+    expect(count).toBe(1); // one segment: [e2 → e3]
+});