fix(restart): use -m nanobot for Windows compatibility

On Windows, sys.argv[0] may be just "nanobot" without full path when
running from PATH. os.execv() doesn't search PATH, causing restart to
fail with "No such file or directory".

Fix by using `python -m nanobot` instead of relying on sys.argv[0].

Fixes #1937

nanobot/agent/loop.py

@@ -292,7 +292,9 @@ class AgentLoop:
 
         async def _do_restart():
             await asyncio.sleep(1)
-            os.execv(sys.executable, [sys.executable] + sys.argv)
+            # Use -m nanobot instead of sys.argv[0] for Windows compatibility
+            # (sys.argv[0] may be just "nanobot" without full path on Windows)
+            os.execv(sys.executable, [sys.executable, "-m", "nanobot"] + sys.argv[1:])
 
         asyncio.create_task(_do_restart())