Ask Logue part 3: MCP server support

[shanforge]

Part 3 of #56. Closes #55.

Two directions: an MCP server so other agents can query Logue, and MCP client support so the
user can add their own servers and the agent can call them. There is no MCP code in the tree
today.

Depends on part 1 — tools added here must appear on both surfaces, which is only one piece of
work once the pipeline is shared.

Scope

• Settings: add, edit, remove a server; per-server enable
• Tools discovered from a server appear in the registry alongside the built-ins, and obey
  the existing per-tool disable list
• Namespaced so a server cannot shadow a built-in tool name
• Destructive tools from a server route through the same approval gate — a remote tool is
  not more trusted than a local one
• Failure is visible and local: an unreachable server disables its tools and says so,
  rather than failing a turn
• Privacy: an MCP server is a network egress. Off by default, named plainly in Settings,
  and the Privacy tab says exactly what leaves the machine
• Timeouts and response size bounded; tool output sanitised before it reaches a prompt
• Works from both surfaces, because of part 1

Why the privacy boxes are not optional

Logue's stated posture is that nothing leaves the laptop by default. An MCP server is network
egress, so it has to be off by default, named plainly, and described in the Privacy tab —
otherwise the claim in the README stops being true.