MCP Driver part 2: Streamable HTTP transport

[dgenio]

Parent: #41 | Split: Streamable HTTP transport

Problem

This is part 2 of #41 (MCP Driver). It covers the Streamable HTTP transport — connecting to remote MCP servers over HTTP — and reconnection handling for long-lived connections.

Depends on the core MCPDriver + stdio transport (part 1).

Proposed Change

1. Streamable HTTP transport

• Connect to remote MCP servers via mcp.client.streamable_http.streamable_http_client.
• Factory method: MCPDriver.from_http(url).
• Handle reconnection for long-lived HTTP connections.
• Clean shutdown via async with protocol.

2. Extended response handling

• Support structured output (structuredContent) when available.
• Handle HTTP-specific errors (timeouts, connection drops) with retry logic.

Acceptance Criteria

• MCPDriver.from_http() connects to a Streamable HTTP MCP server
• HTTP reconnection works for dropped connections
• Structured output (structuredContent) is properly handled
• Integration test with mock HTTP MCP server
• docs/integrations.md updated with real usage examples for both transports

Affected Files

• src/agent_kernel/drivers/mcp.py (extend with HTTP transport)
• tests/test_drivers.py (HTTP transport tests)
• docs/integrations.md (usage examples)

Dependencies

• Requires MCP Driver part 1 (stdio transport + core)