fix: reject pending LSP requests when server closes unexpectedly

When an LSP server dies before responding, _read_stdout hits EOF and
exits silently, leaving pending request Futures unresolved and callers
(e.g. process.stop()'s send.shutdown()) hung forever. Caught by Zuban on
Linux CI: pool.cleanup() hung the Tests workflow for 20 minutes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Mazyod

lsp_types/process.py

@@ -319,6 +319,17 @@ async def _read_stdout(self) -> None:
             return
         except Exception:
             logger.exception("Client - Error reading stdout")
+        finally:
+            # Server closed the connection (EOF, crash, or task cancel) — reject
+            # any outstanding requests so callers don't await forever.
+            for future in list(self._pending_requests.values()):
+                if not future.done():
+                    future.set_exception(
+                        Error(
+                            types.ErrorCodes.InternalError,
+                            "LSP server closed connection before responding",
+                        )
+                    )
 
     async def _read_stderr(self) -> None:
         """Read and log messages from the server's stderr."""