Add Webex bot integration as a channel plugin supporting:
- Bot token authentication via Webex Developer Portal
- Webhook-based message receiving (messages:created events)
- HMAC-SHA1 signature verification for webhook security
- Direct message and group/space messaging
- Media attachment support (images, files)
- Pairing mode for DM authorization
- Multi-account support
Includes:
- Full onboarding wizard for bot configuration
- Probe functionality for connection testing
- Channel status reporting
- Documentation at docs/channels/webex.md
- GitHub labeler configuration
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
