fix: only suggest re-authentication for auth-related HTTP errors

When an HttpError occurs in Google Tasks tools, the error handler now checks
the HTTP status code before suggesting re-authentication. Re-auth messages are
only shown for 401 (Unauthorized) and 403 (Forbidden) errors.

This prevents misleading re-authentication suggestions for non-auth errors like
400 (Bad Request) with malformed arguments, allowing the LLM to focus on the
actual root cause instead of being misdirected by incorrect auth guidance.

The fix applies to both CLI mode (stdio legacy oauth) and MCP mode (OAuth 2.1).

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

gtasks/tasks_tools.py

@@ -25,7 +25,11 @@ LIST_TASKS_MAX_POSITION = "99999999999999999999"
 
 
 def _format_reauth_message(error: Exception, user_google_email: str) -> str:
-    base = f"API error: {error}. You might need to re-authenticate."
+    base = f"API error: {error}"
+
+    # Only suggest re-authentication for auth-related errors (401, 403)
+    if isinstance(error, HttpError) and error.resp.status in (401, 403):
+        base += ". You might need to re-authenticate."
         if is_oauth21_enabled():
             if is_external_oauth21_provider():
                 hint = (
@@ -44,6 +48,8 @@ def _format_reauth_message(error: Exception, user_google_email: str) -> str:
             )
         return f"{base} {hint}"
 
+    return base
+
 
 class StructuredTask:
     def __init__(self, task: Dict[str, str], is_placeholder_parent: bool) -> None: