refactor: unify respond() call after if/else to avoid 3.14 phantom trace

Python 3.14's compiler attributes the async trampoline's CLEANUP_THROW
instructions (for the try-body's await) to the next physical line of
code, which was the else body. coverage.py traced a phantom line event
there, tripping strict-no-cover even though the else never runs.

Moving the try/respond after the if/else avoids the misattribution and
also deduplicates the two respond() calls.

Author: maxisbey

src/mcp/server/lowlevel/server.py

@@ -489,17 +489,18 @@ async def _handle_request(
                 if raise_exceptions:  # pragma: no cover
                     raise err
                 response = types.ErrorData(code=0, message=str(err))
-
-            try:
-                await message.respond(response)
-            except anyio.ClosedResourceError:
-                # Transport closed between handler unblocking and respond. Happens
-                # when _receive_loop's finally wakes a handler blocked on
-                # send_request: the handler runs to respond() before run()'s TG
-                # cancel fires, but after _receive_loop closed _write_stream.
-                logger.debug("Response for %s dropped - transport closed", message.request_id)
         else:  # pragma: no cover
-            await message.respond(types.ErrorData(code=types.METHOD_NOT_FOUND, message="Method not found"))
+            response = types.ErrorData(code=types.METHOD_NOT_FOUND, message="Method not found")
+
+        try:
+            await message.respond(response)
+        except anyio.ClosedResourceError:
+            # Transport closed between handler unblocking and respond. Happens
+            # when _receive_loop's finally wakes a handler blocked on
+            # send_request: the handler runs to respond() before run()'s TG
+            # cancel fires, but after _receive_loop closed _write_stream.
+            logger.debug("Response for %s dropped - transport closed", message.request_id)
+            return
 
         logger.debug("Response sent")