Add timeouts to remote MCP initialization and tool calls

[dgageot]

Prevent the agent from hanging indefinitely when a remote MCP server accepts a TCP connection but never responds.

Three timeout constants are introduced:

• mcpInitTimeout (2 min): caps the initialization handshake (connect + initialize) in doStart
• mcpCallToolTimeout (10 min): caps individual tool calls (generous because tools can be long-running)
• mcpListTimeout (1 min): caps ListTools, ListPrompts, and GetPrompt

The init timeout is applied via a derived context in doStart. The operation timeouts are applied in sessionClient so they cover both stdio and remote transports.

[docker-agent]

Review Summary

Assessment: 🟢 APPROVE

The timeout implementation is well-designed and addresses the core issue of preventing indefinite hangs when remote MCP servers accept connections but never respond. The code correctly applies timeouts at appropriate layers and follows Go best practices for context handling.

Summary

This PR successfully adds three timeout constants to prevent the agent from hanging:

• mcpInitTimeout (2 min): initialization handshake
• mcpCallToolTimeout (10 min): individual tool calls
• mcpListTimeout (1 min): list operations

The implementation is sound with proper defer cancel() patterns and correct timeout propagation. One minor observation about iterator usage patterns is noted below, but it does not block approval.

Findings

One low-severity observation about the iterator wrapper pattern: