Features:
- New predicate rules: NotContains, AnyOf, NoneOf
- Conditional predicates via when clauses (WhenCondition/CompiledWhenCondition)
- Null handling: YAML null treated as absent for exists/not_exists
- Solon agent for rulespec authoring (agents/solon.md)
- Rulespec schema documentation (prompts/schemas/rulespec.schema.md)
Bugfix:
- Fixed when condition evaluation in datalog path: catch-all branch did
naive string contains instead of delegating to evaluate_predicate_datalog().
Rules like matches (regex) were silently ignored, causing vacuous pass
and letting violations through. Now delegates to evaluate_predicate_datalog()
which handles all 12 rule types correctly.
Tests: 34 new tests covering all new rules, null handling, when conditions,
and the when+matches bugfix (butler rulespec pattern).
edbae60ff3