- Add withRuleSnapshot(Map) wither to AlertInstance (same pattern as other withers)
- Call snapshotRule(rule) + withRuleSnapshot in both applyResult (single-firing) and
applyBatchFiring paths so every persisted instance carries a non-empty JSONB snapshot
- Strip null values from the Jackson-serialized map before wrapping in the immutable
snapshot so Map.copyOf in the compact ctor does not throw NPE on nullable rule fields
- Add ruleSnapshotIsPersistedOnInstanceCreation IT: asserts name/severity/conditionKind
appear in the rule_snapshot column after a tick fires an instance
- Add historySurvivesRuleDelete IT: fires an instance, deletes the rule, asserts
rule_id IS NULL and rule_snapshot still contains the rule name (spec §5 guarantee)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>