Refactored PromptBuilder to support both legacy (sync) and new (async)
optimization paths:
Legacy (backward compatible):
- cache_metrics() still uses sync ContextOptimizer
- build_cache_aligned() unchanged, no optimization
New (pluggable OptimizerService):
- cache_metrics() falls back gracefully to ContextOptimizer
- NEW: build_cache_aligned_async() uses pluggable service
- Custom optimizers now work in prompt building
Architecture Benefits:
✅ Generic registry optimization works everywhere (ingest + query)
✅ Same codebase supports multiple compressors
✅ Async-aware for production query paths
✅ Backward compatible (no breaking changes)
Usage in query_executor:
Tests: All 14 prompt tests passing (no changes to test surface)