Summary

This MR adds a new public API method CqlEngine.resolveParameterDefault() that allows callers to resolve the CQL-defined default value of a named parameter without manipulating engine internals.

1. New CqlEngine.resolveParameterDefault(VersionedIdentifier, String, ZonedDateTime?): Any? method that resolves a library, finds the named ParameterDef, and evaluates its default expression using the standard engine lifecycle (init / beginEvaluation / endEvaluation / exitLibrary), with proper error handling via processException(). Returns null if the parameter has no default.
2. No changes to State.kt -- the implementation reuses existing state lifecycle methods rather than introducing new low-level stack manipulation methods, consistent with the architecture established in commits 23f71e39 (evaluate API refactor) and 2803f628 (class name simplification).
3. Comprehensive test coverage via ResolveParameterDefaultTest (8 tests) exercising the measurement-period interval scenario, parameters without defaults, integer defaults, Now() evaluation with custom evaluationDateTime, error cases, and state isolation between resolveParameterDefault() and evaluate() calls.

Code Review Suggestions

• Verify that calling state.init(library) (which asserts stack.isEmpty()) is safe in all realistic call sequences from clinical-reasoning. If clinical-reasoning ever calls resolveParameterDefault while the engine state is not clean (e.g., mid-evaluation), the assertion will fail. Confirm the upstream caller (MeasureProcessorTimeUtils) always calls this before any evaluate().
• The method uses environment.resolveLibrary(libraryIdentifier) which bypasses the multi-library loadAndValidate() path and its structured error collection. Confirm this is acceptable -- the assumption is the library is already compiled/loaded by the time a caller wants to inspect parameter defaults.
• The evaluationVisitor property is @Deprecated. This method encapsulates its usage, but confirm no linting or Sonar rules will flag the internal usage (the clinical-reasoning side will drop its @SuppressWarnings once migrated).
• Check whether state.endEvaluation() in the finally block can throw if beginEvaluation() was not reached (e.g., if state.init(library) throws due to a failed assertion). If so, the cleanup in finally could mask the original exception.