fix(backend/copilot): use resolved path for bridging, explicit return None

- Pass `resolved` (realpath-expanded) to `_bridge_to_sandbox` in
  `_read_file_handler` so the bridge target matches the file that was
  actually read (addresses review comment).
- Replace bare `return` with explicit `return None` in
  `_bridge_to_sandbox` large-file skip path for consistency with the
  declared `str | None` return type.

autogpt_platform/backend/backend/copilot/sdk/e2b_file_tools.py

@@ -355,7 +355,7 @@ async def _bridge_to_sandbox(
                 file_size,
                 basename,
             )
-            return
+            return None
         with open(expanded, "rb") as fh:
             content = fh.read()
         if file_size <= _BRIDGE_SHELL_MAX_BYTES:

autogpt_platform/backend/backend/copilot/sdk/tool_adapter.py

@@ -393,7 +393,7 @@ async def _read_file_handler(args: dict[str, Any]) -> dict[str, Any]:
         text = "".join(selected)
         sandbox = _current_sandbox.get(None)
         if sandbox is not None:
-            bridged = await _bridge_to_sandbox(sandbox, file_path, offset, limit)
+            bridged = await _bridge_to_sandbox(sandbox, resolved, offset, limit)
             if bridged:
                 text += f"\n[Sandbox copy available at {bridged}]"
         return _mcp_ok(text)