fix: strip smart quotes and zero-width chars from pasted URLs

normalizeUrl now strips smart quotes, zero-width spaces, and other invisible
formatting characters that browsers inject when copy-pasting URLs from rich
text sources. Prevents false "URL invalid" errors for valid URLs.

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

frontend/src/__tests__/sources-utils.test.ts

@@ -32,6 +32,21 @@ describe('normalizeUrl', () => {
   it('should handle URLs with www prefix', () => {
     expect(normalizeUrl('www.example.com')).toBe('https://www.example.com');
   });
+
+  it('should strip smart quotes from copy-pasted URLs', () => {
+    expect(normalizeUrl('\u201Chttps://example.com\u201D')).toBe('https://example.com');
+    expect(normalizeUrl('\u2018example.com\u2019')).toBe('https://example.com');
+  });
+
+  it('should strip zero-width characters', () => {
+    expect(normalizeUrl('https://example.com\u200B')).toBe('https://example.com');
+    expect(normalizeUrl('\uFEFFhttps://example.com')).toBe('https://example.com');
+  });
+
+  it('should handle .ai TLD with path', () => {
+    expect(normalizeUrl('https://awesomeagents.ai/news/')).toBe('https://awesomeagents.ai/news/');
+    expect(normalizeUrl('awesomeagents.ai/news/')).toBe('https://awesomeagents.ai/news/');
+  });
 });
 
 describe('isValidUrl', () => {

frontend/src/pages/Sources.tsx

@@ -23,15 +23,22 @@ import LoadingSpinner from '~/components/ui/LoadingSpinner';
  * Prepend https:// if the URL has no scheme.
  */
 export function normalizeUrl(url: string): string {
-  const trimmed = url.trim();
-  if (!trimmed) return trimmed;
+  // Strip smart quotes, zero-width chars, and other invisible formatting
+  // that browsers or rich-text editors inject when copy-pasting URLs
+  const cleaned = url
+    .trim()
+    .replace(/[\u200B-\u200D\uFEFF\u00A0]/g, '') // zero-width & non-breaking spaces
+    .replace(/^[\u201C\u201D\u201E\u201F\u2018\u2019\u00AB\u00BB"']+/, '') // leading quotes
+    .replace(/[\u201C\u201D\u201E\u201F\u2018\u2019\u00AB\u00BB"']+$/, '') // trailing quotes
+    .trim();
+  if (!cleaned) return cleaned;
   if (
-    !trimmed.startsWith('http://') &&
-    !trimmed.startsWith('https://')
+    !cleaned.startsWith('http://') &&
+    !cleaned.startsWith('https://')
   ) {
-    return 'https://' + trimmed;
+    return 'https://' + cleaned;
   }
-  return trimmed;
+  return cleaned;
 }
 
 /**