Feature Request: Microsoft Teams integration

## Summary
Add a Microsoft Teams integration for Blink agents, mirroring the existing Slack integration (`@blink-sdk/slack`).

## Motivation
Many organizations use MS Teams as their primary communication platform. Supporting Teams would significantly expand Blink's reach and allow agents to be deployed where these teams already work.

## Proposed Scope
- New `@blink-sdk/teams` package (mirroring `packages/slack/`)
- Bot Framework activity handler (equivalent to `Receiver`)
- AI SDK tools: sendMessage, readMessages, readThreadReplies, getUserInfo, reactToMessage, reportStatus
- Message formatting for Teams (Adaptive Cards / Teams markdown)
- File attachment support via Graph API
- Scout agent wiring (`lib/teams.ts`) + `TeamsConfig` in `ScoutOptions`
- Webhook route (`/teams`) in agent entry point

## Key Technical Considerations
- Azure AD app registration for auth (client ID/secret vs Slack's bot token/signing secret)
- Bot Framework SDK (`botbuilder`) + MS Graph API for channel/message operations
- Teams threading model differs from Slack's `thread_ts` approach
- Adaptive Cards for rich content (vs Slack blocks)
- SharePoint/OneDrive file handling (vs Slack file API)
- Stricter rate limits than Slack
- Proactive messaging requires stored conversation references