a11y: navigation badges missing aria-live regions

[boldsbrainai]

Summary

The navigation badges (#badge-sessions, #badge-antipatterns, #badge-output) are updated dynamically via setBadge() in app.ts but have no aria-live attribute. Screen readers do not announce badge count changes to keyboard-only or assistive technology users.

Location

src/webview/app.ts — setBadge() function

Fix

Add aria-live="polite" and aria-atomic="true" to the badge container elements rendered in the navigation HTML.

Effort estimate

~30 minutes