Add BF-SDK to Agents-for-js migration skill

[Joel Mut (sw-joelmut)]

Fixes #654

Summary

Adds a skill for migrating JavaScript/TypeScript bots from Bot Framework SDK to Microsoft 365 Agents SDK.

Changes

• Adds assessment-first migration workflow
• Adds Bot Framework → Agents SDK migration map
• Classifies migrations as Direct, Rewrite, Decision, or Unsupported
• Covers handlers, state, dialogs, hosting, auth, proactive messaging, agent-to-agent, named pipes, and Teams
• Requires stable SDK API verification and explicit user approval before implementation
• Defines validation and reporting requirements

Testing

The following images show the workflow and two of the migrated samples working.