refactor: move MCP service from api/routes to agent package

MCP is an optional AI feature that already depends on
agent.gns3_copilot (Gns3Connector, nornir/netmiko tools) and whose
MCP_AVAILABLE feature flag lives in gns3server/agent. Moving it there
collocates all AI features under one tree and removes AI code from the
core REST routes.

- git mv gns3server/api/routes/mcp -> gns3server/agent/mcp (no content changes)
- api/server.py, core/tasks.py: update import paths
- tests: tests/api/routes/mcp -> tests/agent/mcp, rewrite patch BASE and
  handler imports; fix MCP_DIR depth in test_tool_params.py
- agent/__init__.py: probe the SDK via importlib.import_module so the
  top-level name "mcp" is not bound in the agent namespace (it would
  shadow the new gns3server.agent.mcp subpackage and break
  'from gns3server.agent import mcp')
- docs: update source file paths

Verified: full suite 1567 passed; 82 MCP tools registered, SSE mounted
at /v3/mcp/transport.

gns3server/agent/mcp/server.py

@@ -0,0 +1,50 @@
+#
+# Copyright (C) 2026 GNS3 Technologies Inc.
+# Author: Yue Guobin
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""
+MCP tool handlers for GNS3 server information.
+"""
+
+from typing import Any
+
+import logging
+
+log = logging.getLogger(__name__)
+
+
+# ── Helper ─────────────────────────────────────────────────────────────────
+
+def _get_connector(gns3_ctx: dict[str, Any]):
+    from gns3server.agent.gns3_copilot.gns3_client.custom_gns3fy import Gns3Connector
+    return Gns3Connector(
+        url=gns3_ctx["server_url"],
+        jwt_token=gns3_ctx["jwt_token"],
+        api_version=3,
+        verify=False,
+    )
+
+
+# ── Tool handlers ──────────────────────────────────────────────────────────
+
+def get_version_handler(params: dict[str, Any], gns3_ctx: dict[str, Any]) -> dict[str, Any]:
+    conn = _get_connector(gns3_ctx)
+    return conn.http_call("get", f"{conn.base_url}/version").json()
+
+
+def get_statistics_handler(params: dict[str, Any], gns3_ctx: dict[str, Any]) -> dict[str, Any]:
+    conn = _get_connector(gns3_ctx)
+    return conn.http_call("get", f"{conn.base_url}/statistics").json()