fix: align browser property with base class and remove dead env writes

- shipyard_neo: browser property now returns None when not initialized
  instead of raising RuntimeError, matching ComputerBooter base contract
- computer_tool_provider: remove dead os.environ writes for shipyard
  (SHIPYARD_ENDPOINT / SHIPYARD_ACCESS_TOKEN are never read anywhere)
  and remove unused os import

astrbot/core/computer/booters/shipyard_neo.py

@@ -474,9 +474,7 @@ class ShipyardNeoBooter(ComputerBooter):
         return self._shell
 
     @property
-    def browser(self) -> BrowserComponent:
-        if self._browser is None:
-            raise RuntimeError("ShipyardNeoBooter is not initialized.")
+    def browser(self) -> BrowserComponent | None:
         return self._browser
 
     async def upload_file(self, path: str, file_name: str) -> dict:

astrbot/core/computer/computer_tool_provider.py

@@ -12,7 +12,6 @@ does not require changes here.
 
 from __future__ import annotations
 
-import os
 import platform
 from functools import cache
 from typing import TYPE_CHECKING
@@ -202,8 +201,6 @@ class ComputerToolProvider:
             if not ep or not at:
                 logger.error("Shipyard sandbox configuration is incomplete.")
                 return []
-            os.environ["SHIPYARD_ENDPOINT"] = ep
-            os.environ["SHIPYARD_ACCESS_TOKEN"] = at
 
         # Always return the full tool set for schema stability
         return get_default_sandbox_tools(ctx.sandbox_cfg)