Move verbose checklist from hook reason into SKILL.md system context

[micahstubbs]

Summary

• Moves the full completion checklist (6 items + behavioral instructions) from the hook's reason field into SKILL.md
• Reduces the hook's block reason to a single line: TASKMASTER (N): Stop blocked. Follow the taskmaster completion checklist. Done signal: TASKMASTER_DONE::<session_id>
• Bumps version to 2.2.0

Problem

The hook's reason field is displayed as a visible message in the Claude Code session history every time the stop is blocked. The previous ~30 line checklist (re-read user messages, check task list, check plan, check for errors, check for loose ends, check for blockers, honesty check, DO NOT NARRATE, etc.) was polluting the conversation transcript and making it hard to read actual human prompts and model outputs.

Solution

The key insight is that SKILL.md content is loaded as system context — it's available to the model but invisible as messages in the session history. So the architecture is now:

Component	Contains	Visible in session history?
SKILL.md	Full completion checklist + behavioral instructions	No (system context)
Hook reason	Brief trigger with counter, status, and done signal	Yes (one clean line)

The model still has access to all the same instructions via the skill's system context, so behavior is unchanged. The session transcript is now readable.

Changes

• SKILL.md: Added "Completion Checklist" section with the full behavioral instructions previously in the hook reason
• hooks/check-completion.sh: Reduced reason to one-liner referencing the skill checklist
• check-completion.sh: Same change applied to root-level variant
• docs/SPEC.md: Updated to document the new prompt architecture