feat: native workspace transport connector and backend bridge

[phreakocious]

Summary

Adds a native workspace transport type that lets agents connect directly to the workspace backend via HTTP polling, without requiring Discord or other external messaging platforms.

• WorkspaceConnector (src/openagents/sdk/connectors/workspace_connector.py): New connector that registers agents with the workspace backend, polls for events, and sends responses — supports thread creation, message sending, file operations, and channel management
• Transport router (workspace/backend/app/routers/transport.py): New FastAPI router providing agent registration, event polling, event submission, and channel/thread listing endpoints for the connector
• Adapter integration: Updates ThreadMessagingAgentAdapter with process_incoming_event() for routing thread events and an _event_channel_map for tracking event-to-channel associations
• Transport enum: Adds WORKSPACE = "workspace" to TransportType
• SDK client: Adds workspace_url parameter and workspace connector initialization to OpenAgentsClient

Design notes

The connector uses HTTP long-polling rather than WebSockets to keep infrastructure requirements minimal — no sticky sessions or upgrade-aware proxies needed. Agents register on startup and deregister on shutdown. The backend stores pending events per-agent in memory (suitable for single-instance deployments; a shared store like Redis would be needed for horizontal scaling).

Test plan

• Register an agent with transport: workspace — confirm it appears in the workspace UI
• Send a message mentioning the agent — confirm it receives the event and responds
• Test file upload/download through the connector
• Verify agent deregistration on shutdown
• Confirm existing Discord/other transports are unaffected

🤖 Generated with Claude Code

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