fix: reduce the default tool return to something more sane [LET-4180] (#4383)

fix: reduce the default tool return to something more sane (prev limit was allowing like 200k tokens to come through and crash gpt-5

Author: cpacker

letta/constants.py

@@ -340,7 +340,7 @@ def FUNCTION_RETURN_VALUE_TRUNCATED(return_str, return_char: int, return_char_li
 
 # Function return limits
 FUNCTION_RETURN_CHAR_LIMIT = 50000  # ~300 words
-BASE_FUNCTION_RETURN_CHAR_LIMIT = 1000000  # very high (we rely on implementation)
+BASE_FUNCTION_RETURN_CHAR_LIMIT = 50000  # same as regular function limit
 FILE_IS_TRUNCATED_WARNING = "# NOTE: This block is truncated, use functions to view the full content."
 
 MAX_PAUSE_HEARTBEATS = 360  # in min