fix(mcp): re-register tools after a parked server is revived

_discover_tools only filled self._tools; registry registration happened
only in _discover_and_register_server (initial start) and _refresh_tools.
After parking deregistered a server's tools, a revival rebuilt the
transport but published zero tools — a phantom recovery.

Register freshly discovered tools whenever _ready is set and the
registry entry list is empty. Extracted from PR #54139 by @nicha16
(the remainder of that PR reverses the park design and is not taken).

tools/mcp_tool.py

@@ -2340,6 +2340,7 @@ class MCPServerTask:
                 self.name,
             )
             self._tools = []
+            self._register_discovered_tools_if_needed()
             return
         async with self._rpc_lock:
             tools_result = await self.session.list_tools()
@@ -2348,6 +2349,23 @@ class MCPServerTask:
             if hasattr(tools_result, "tools")
             else []
         )
+        self._register_discovered_tools_if_needed()
+
+    def _register_discovered_tools_if_needed(self) -> None:
+        """Re-register tools after a post-ready reconnect if needed.
+
+        Initial registration is performed by ``_discover_and_register_server``
+        after ``start()`` completes. During a later reconnect, however,
+        ``_ready`` remains set; if outage handling previously deregistered
+        stale tools (parking calls ``_deregister_tools``), a successful
+        revival must publish the freshly discovered tools again — otherwise
+        the transport comes back alive with zero registered tools.
+        """
+        if not self._ready.is_set() or self._registered_tool_names:
+            return
+        self._registered_tool_names = _register_server_tools(
+            self.name, self, self._config
+        )
 
     async def run(self, config: dict):
         """Long-lived coroutine: connect, discover tools, wait, disconnect.