fix: Strip trailing slashes before route pattern matching

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: nicohrubec

packages/tanstackstart-react/src/server/routeParametrization.ts

@@ -29,8 +29,9 @@ function patternToRegex(pattern: string): RegExp {
  * Patterns are expected to be pre-sorted by specificity (more segments first, static before dynamic).
  */
 export function matchUrlToRoutePattern(pathname: string, patterns: string[]): string | undefined {
+  const normalizedPathname = pathname.length > 1 ? pathname.replace(/\/$/, '') : pathname;
   for (const pattern of patterns) {
-    if (patternToRegex(pattern).test(pathname)) {
+    if (patternToRegex(pattern).test(normalizedPathname)) {
       return pattern;
     }
   }

packages/tanstackstart-react/test/server/routeParametrization.test.ts

@@ -38,4 +38,9 @@ describe('matchUrlToRoutePattern', () => {
     const patternsNested = ['/users/$id/profile', '/users/$id'];
     expect(matchUrlToRoutePattern('/users/123/profile', patternsNested)).toBe('/users/$id/profile');
   });
+
+  it('handles URLs with trailing slashes', () => {
+    expect(matchUrlToRoutePattern('/page-a/', patterns)).toBe('/page-a');
+    expect(matchUrlToRoutePattern('/page-b/42/', patterns)).toBe('/page-b/$id');
+  });
 });