feat: add credential capture with bar/toast prompts

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

extension/src/content/detector.ts

@@ -6,6 +6,7 @@
 
 import { setupFillListener } from './fill';
 import { injectFieldIcons } from './icon';
+import { hookForms } from './capture';
 
 /// Find password fields on the page and detect their associated username inputs.
 function detectLoginForms(): Array<{ password: HTMLInputElement; username: HTMLInputElement | null }> {
@@ -80,6 +81,7 @@ function scan(): void {
   for (const { password, username } of forms) {
     injectFieldIcons(password, username);
   }
+  hookForms();
 }
 
 // --- Initialization ---