feat(api): implement MCP server #91

Goal

Implement the MCP (Model Context Protocol) server adapter so AI agents and MCP clients can interact with paiOS programmatically.

Scope

In scope:

• MCP server exposing engine capabilities as tools
• Feature-gated behind api_mcp_server
• Tool discovery (GetTools / list capabilities)
• Basic tool execution routing to core ports
• Server context and description (relates to feat(api): implement and document MCP Server context (description, GetTools) #53)

Out of scope:

• MCP client (M0.3 / M2)
• Complex tool orchestration
• Authentication / per-client permissions

Done when

• MCP server starts and responds to tool discovery
• At least one tool (e.g. text completion) is callable
• Tools map 1:1 to engine primitives (design discipline per docs(api): MCP Server tools as 1:1 primitives (design discipline) #58)
• Feature-gated, compiles with and without
• cargo clippy clean

Related

Subsumes: #50 (MCP flow control tools), #53 (MCP server context)