Feature: Enable specific MCP servers for sub-agents

Feature Request

When spawning sub-agents via the Task tool, it would be useful to be able to enable specific MCP servers just for that agent, independent of the main session's MCP server state.

Use Case

• Disable a verbose/expensive MCP server in the main conversation to save context
• Still allow a focused sub-agent to use that MCP server for a specific task
• Better separation of concerns (e.g., database exploration agent gets DB MCPs, code review agent only needs file tools)

Current Behavior

MCP server state is session-wide. Disabling an MCP server affects the main conversation and all sub-agents.

Proposed Behavior

Add an optional parameter to the Task tool (e.g., mcp_servers: ["github", "database"]) that would enable specific MCP servers for that sub-agent, regardless of the main session's state.