Sign in to MCP presets from the connect wizard

Notion, Linear, Atlassian, Sentry, Asana and Stripe no longer open the
MCP server form. The wizard shows one "Sign in to Notion" button: the
pop-up opens inside the click (so browsers allow it), follows the
worker's mcp.oauth events to the provider, and the tool is saved on
success with its actions on the done step. Reconnecting a preset uses
the same flow, as do the chat bar and the health toast.

Saving an OAuth MCP server without a new handshake now uses the stored
sign-in instead of failing, and the custom MCP form keeps scopes and
timeout under Show advanced.

tests/api/user/test_tools_mcp_pg.py

@@ -328,7 +328,10 @@ class TestMCPServerSave:
     def test_oauth_missing_task_id_returns_400(self, app):
         from docsgpt.api.user.tools.mcp import MCPServerSave
 
-        with app.test_request_context(
+        # No OAuth task and no stored sign-in that works.
+        unauthorized = MagicMock()
+        unauthorized.discover_tools.side_effect = RuntimeError("401")
+        with patch("docsgpt.api.user.tools.mcp.MCPTool", return_value=unauthorized), app.test_request_context(
             "/api/mcp_server/save", method="POST",
             json={
                 "displayName": "Srv",
@@ -344,6 +347,31 @@ class TestMCPServerSave:
             response = MCPServerSave().post()
         assert response.status_code == 400
 
+    def test_oauth_without_task_uses_the_stored_sign_in(self, app, pg_conn):
+        """Signed in before: the server answers with the saved tokens, no new handshake."""
+        from docsgpt.api.user.tools.mcp import MCPServerSave
+
+        signed_in = MagicMock()
+        signed_in.get_actions_metadata.return_value = [{"name": "search"}]
+        with _patch_db(pg_conn), patch(
+            "docsgpt.api.user.tools.mcp.MCPTool", return_value=signed_in,
+        ), patch("docsgpt.api.user.tools.mcp._mcp_connection", return_value=None), app.test_request_context(
+            "/api/mcp_server/save", method="POST",
+            json={
+                "displayName": "Linear",
+                "config": {
+                    "transport_type": "http",
+                    "server_url": "https://mcp.linear.app/mcp",
+                    "auth_type": "oauth",
+                },
+            },
+        ):
+            from flask import request
+            request.decoded_token = {"sub": "u-signed-in"}
+            response = MCPServerSave().post()
+        assert response.status_code == 200
+        signed_in.discover_tools.assert_called_once()
+
     def test_creates_mcp_tool_successfully(self, app, pg_conn):
         from docsgpt.api.user.tools.mcp import MCPServerSave