feat(browser-agent): Add updated BT broadband workflow example

New example file uses the latest workflow format with:
- Variables section with sample test values
- if/try/sequence workflow control structures
- Progressive escalation for address matching
- Vision LLM fallback for complex interactions
- Comprehensive extraction logic

This is a ready-to-run example based on the production template.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: guyernest