Add scoped nested rules

[sydneygrivers]

Added Scoped Nested Rules Feature

1. New ScopedAlmanac class (src/scoped-almanac.js)
   - Wraps a parent almanac with a specific array item context
   - Allows conditions inside nested rules to access properties directly on the current array item
   - Supports resolvePath() to resolve JSONPath directly on the scoped item
   - Falls back to parent almanac for facts not found on the item
2. New some operator for nested conditions (src/condition.js)
   - Added isNestedCondition() - detects operator: 'some' with a conditions property
   - Added isScopedCondition() - detects path-only conditions (no fact, just path + operator)
   - Scoped conditions work inside nested blocks where the "fact" is implicitly the current array item
3. Updated rule evaluation (src/rule.js)
   - Added evaluateNestedCondition() to iterate over array items
   - Creates a ScopedAlmanac for each array item and evaluates nested conditions against it
   - Short-circuits on first match (returns true as soon as any item matches)
   - Threaded currentAlmanac through all evaluation functions (evaluateCondition, all, any, not, realize, etc.)
4. Error handling (src/almanac.js)
   - Added resolvePath() stub that throws helpful error if path-only conditions are used outside nested context
5. TypeScript definitions (types/index.d.ts) - Updated types to support the new structures
6. Comprehensive tests (test/engine-nested-conditions.test.js) - ~1100 lines of test coverage