* Address review: escape quotes in filter paths, type-safe tests

- filterExpression: escape single quotes in keys and values to prevent
  invalid JSONPath; throw if filterKey is a function (must be resolved)
- Test: rename to clarify bracket-notation behavior, use FunctionKey
  type and Operation enum instead of 'as any' casts

* Bump version to 5.0.0-alpha.5

* Add coverage for quote escaping in filter paths

- Add tests for single quotes in identity key names and values
- Narrow filterExpression param type to string (callers always resolve)

* Narrow filterExpression value type to string (key is always string)