Use deterministic workspace dir for EclipseJDTLS to enable cache reuse (#1214)

* Use deterministic workspace dir for EclipseJDTLS to enable cache reuse

Replace uuid.uuid4().hex with a hash of the project path for the JDTLS
workspace directory. This allows the workspace cache (project index,
shared index, configuration) to be reused across server restarts instead
of rebuilding from scratch each time.

The random UUID was inherited from microsoft/multilspy (a research/testing
library where ephemeral workspaces made sense), but for Serena's use case
— long-lived projects with repeated restarts — deterministic workspace
paths significantly reduce startup time, especially for large Java projects.

* Fix import sort order for ruff lint

src/solidlsp/language_servers/eclipse_jdtls.py

@@ -3,12 +3,12 @@ Provides Java specific instantiation of the LanguageServer class. Contains vario
 """
 
 import dataclasses
+import hashlib
 import logging
 import os
 import pathlib
 import shutil
 import threading
-import uuid
 from pathlib import PurePath
 from time import sleep
 from typing import cast
@@ -276,13 +276,16 @@ class EclipseJDTLS(SolidLanguageServer):
             )
 
         def create_launch_command(self) -> list[str]:
-            # ws_dir is the workspace directory for the EclipseJDTLS server
+            # ws_dir is the workspace directory for the EclipseJDTLS server.
+            # Use a deterministic hash of the project path so the workspace
+            # (and its cached index) can be reused across restarts.
+            project_hash = hashlib.md5(self._repository_root_path.encode()).hexdigest()
             ws_dir = str(
                 PurePath(
                     self._solidlsp_settings.ls_resources_dir,
                     "EclipseJDTLS",
                     "workspaces",
-                    uuid.uuid4().hex,
+                    project_hash,
                 )
             )