feat(desktop): setup_mcp tool — inline MCP consent card over the clarify-style blocking bridge

New desktop_ui tool: the agent proposes an MCP server (install/enable/
authorize + a one-line reason) and blocks on mcp.setup.request until the
renderer's consent card answers mcp.setup.respond with the outcome
(installed/enabled/authorized/declined/unanswered/error). Same lifecycle
as clarify: 10-min timeout, allow_expired late answers, tool lifecycle
events forced on so the card mounts even with tool progress off. Desktop
prompt hint steers the model to the tool instead of hand-editing config;
every other surface keeps the schema out and is pointed at hermes mcp
install.

toolsets.py

@@ -279,6 +279,7 @@ TOOLSETS = {
             "open_preview", "read_preview",
             "read_window_below",
             "focus_pane", "react_to_message",
+            "setup_mcp",
         ],
         "includes": []
     },