Solves the tautology problem where the LLM would write invariants after
implementation, making them match what was done rather than constrain it.
Changes:
- plan_write now accepts 'rulespec' parameter
- New plans REQUIRE rulespec (fails with helpful error if missing)
- Plan updates don't require rulespec (backward compatible)
- Rulespec is parsed, validated, and written atomically with plan
- Updated system prompt with clear examples for new vs update
- Updated tool definition schema
- Updated all affected tests
New flow: task → plan+rulespec → user reviews BOTH → approve → implement
7e2d9bc22c