Four copies of the 40/60 head/tail algorithm with a near-identical notice
(terminal_tool_result, mcp_tool_content, code_execution_tool,
environments/base_output) collapse into tools/tool_output_truncate.py, so the
ratio and the `... [<LABEL> TRUNCATED - N <unit> omitted out of T total] ...`
marker are defined once. execute_code keeps byte mode + spill path and only
shares the notice/split. Visible change: the terminal notice now uses
thousands separators like the other three (`9,000 chars` not `9000 chars`).
kanban_specify._truncate: comment claimed escape stripping the body never did;
comment now says what the plain clamp is for.
1512edfb85