Preserve originating views through detail navigation

tests/unit/navigation-context.test.ts

@@ -0,0 +1,23 @@
+import { describe, expect, it } from 'vitest';
+import { contextHref, returnLabel, safeReturnHref } from '../../src/lib/navigation-context.js';
+
+describe('navigation context', () => {
+    it('retains nested origins, list scope, loaded results and anchors', () => {
+        const source = new URL('http://localhost/leaderboard/players/42?game=t5&offset=25&returnTo=%2Fleaderboard%3Fq%3DAce#history-title');
+        const match = new URL(contextHref('/matches/123', source), source);
+        expect(safeReturnHref(match.searchParams.get('returnTo'), '/matches')).toBe(source.pathname + source.search + source.hash);
+        expect(returnLabel(match.searchParams.get('returnTo')!)).toBe('Back to player');
+        expect(returnLabel('/collections?view=history&launches=30')).toBe('Back to launch history');
+    });
+
+    it('preserves the selected diagnostic tab on both sides of a contextual link', () => {
+        const url = new URL(contextHref('/servers/t5_zombie_theater_1?tab=logs&log=console', '/maintenance/incident?returnTo=%2Fmaintenance%3Fview%3Dactivity'), 'http://localhost');
+        expect(url.searchParams.get('tab')).toBe('logs');
+        expect(url.searchParams.get('log')).toBe('console');
+        expect(url.searchParams.get('returnTo')).toBe('/maintenance/incident?returnTo=%2Fmaintenance%3Fview%3Dactivity');
+    });
+
+    it.each(['//evil.test', 'https://evil.test/', '/api/auth/logout', '/login', '/hosts/../../api/hosts', '/\\evil.test', '/hosts\n/42', '/unknown', '/' + 'x'.repeat(12000)])('rejects unsafe or unsupported return paths: %s', value => {
+        expect(safeReturnHref(value, '/betas')).toBe('/betas');
+    });
+});