fix: use force=True for multiprocessing set_start_method

Prevents RuntimeError when the context has already been set,
e.g. when Terminal.app reuses a tab or the process restarts.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

src/exo/main.py

@@ -254,7 +254,7 @@ def main():
     target = min(max(soft, 65535), hard)
     resource.setrlimit(resource.RLIMIT_NOFILE, (target, hard))
 
-    mp.set_start_method("spawn")
+    mp.set_start_method("spawn", force=True)
     # TODO: Refactor the current verbosity system
     logger_setup(EXO_LOG, args.verbosity)
     logger.info("Starting EXO")