1.8.5

Task-list tool as sole writer (milestone 46)

• A new stdlib-only tool, tools/task_list.py, is now the only writer of TASKS_TODO.md and TASKS_DONE.md once a milestone exists. It has three subcommands: initialize writes the whole ordered task list for /derive-tasks and lands it whole or not at all, insert places one task at the required --end, --before, or --after position for /submit-task, and move moves a finished task to TASKS_DONE.md under its **Verified:** bar.
• Every write re-renders the whole file in one canonical layout and matches task titles exactly (case- and whitespace-insensitive), refusing a partial, duplicate, or unknown title with one Error: line and both files unchanged. A failed move leaves both files as they were.
• Task completion no longer writes ad-hoc scripts to move a task: the complete-task agent and skill run the move chained with their git step in one shell call, so the completion tail is one turn shorter and a refused move stages and commits nothing.
• Measured in field use over 71 task completions after the change against 411 before: moves done by an ad-hoc script fell from 78% to 1%, moves needing more than one write call from 23% to none, the median completion tail from 3 turns to 2 (with 86% of completions now ending in exactly 2), and the tool refused none of its calls. The saving is about 2.5% of a completion agent's cost, most of it in cached input.
• /submit-task stops on an anchor that names no task instead of appending at the end, and /derive-tasks writes its whole list in one call rather than one append per brief.

Full Changelog: 1.8.4...1.8.5