refactor: modularity fixes + plugin registry + compiled research

purpose_agent/__init__.py

@@ -75,6 +75,12 @@ from purpose_agent.hitl import (
 # Evaluation
 from purpose_agent.evaluation import BenchmarkTask, BenchmarkRunner, BenchmarkResult
 
+# Plugin Registry
+from purpose_agent.registry import (
+    PluginRegistry, backend_registry, callback_registry, model_registry,
+    EmbeddingBackend, default_embedding,
+)
+
 __all__ = [
     # Core
     "State", "Action", "Trajectory", "TrajectoryStep", "Heuristic",
@@ -101,4 +107,7 @@ __all__ = [
     "CLIInputHandler", "AutoApproveHandler", "InterruptType",
     # Evaluation
     "BenchmarkTask", "BenchmarkRunner", "BenchmarkResult",
+    # Plugin Registry
+    "PluginRegistry", "backend_registry", "callback_registry", "model_registry",
+    "EmbeddingBackend", "default_embedding",
 ]