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.

tests/tools/test_setup_mcp_tool.py

@@ -0,0 +1,75 @@
+"""setup_mcp tool — the desktop inline MCP consent card's tool half.
+
+Behavior contracts:
+- no callback (not the desktop app) → tool_error pointing at the CLI path
+- empty/invalid args → tool_error
+- callback answer passes through as JSON
+- empty callback answer (timeout) → status "unanswered", never an error
+"""
+
+import json
+
+import pytest
+
+from tools.setup_mcp_tool import setup_mcp_tool
+
+
+def test_requires_desktop_callback():
+    result = json.loads(setup_mcp_tool(server="linear", callback=None))
+    assert "error" in result
+    assert "hermes mcp install" in result["error"]
+
+
+def test_requires_server_name():
+    result = json.loads(setup_mcp_tool(server="  ", callback=lambda *a: ""))
+    assert "error" in result
+
+
+def test_rejects_unknown_action():
+    result = json.loads(
+        setup_mcp_tool(server="linear", action="uninstall", callback=lambda *a: "")
+    )
+    assert "error" in result
+    assert "action" in result["error"]
+
+
+def test_passes_through_renderer_outcome():
+    outcome = {"status": "installed", "server": "linear"}
+
+    def cb(server, action, reason):
+        assert server == "linear"
+        assert action == "install"
+        assert reason == "to read tickets"
+        return json.dumps(outcome)
+
+    result = json.loads(
+        setup_mcp_tool(server="linear", action="install", reason="to read tickets", callback=cb)
+    )
+    assert result == outcome
+
+
+def test_timeout_returns_unanswered_not_error():
+    result = json.loads(setup_mcp_tool(server="figma", callback=lambda *a: ""))
+    assert result["status"] == "unanswered"
+    assert result["server"] == "figma"
+
+
+def test_callback_exception_is_tool_error():
+    def cb(*a):
+        raise RuntimeError("gateway went away")
+
+    result = json.loads(setup_mcp_tool(server="figma", callback=cb))
+    assert "error" in result
+
+
+def test_non_json_answer_wrapped_as_error_status():
+    result = json.loads(setup_mcp_tool(server="figma", callback=lambda *a: "garbage"))
+    assert result["status"] == "error"
+
+
+@pytest.mark.parametrize("action", ["install", "enable", "authorize"])
+def test_all_actions_accepted(action):
+    result = json.loads(
+        setup_mcp_tool(server="x", action=action, callback=lambda s, a, r: json.dumps({"status": "declined", "server": s}))
+    )
+    assert result["status"] == "declined"