feat: add generic review projection and reporting

tests/test_pipeline.py

@@ -219,6 +219,7 @@ def test_duplicate_modifier_ids_fail_during_preflight_before_modification() -> N
     assert result.partial_markdown == "a"
     assert result.changes == ()
     assert result.errors[0].error_type == "PipelineContractError"
+    assert result.errors[0].stage is ErrorStage.PREFLIGHT
 
 
 def test_non_modifier_entry_fails_during_preflight() -> None:
@@ -229,6 +230,7 @@ def test_non_modifier_entry_fails_during_preflight() -> None:
     assert result.status is RunStatus.FAILED
     assert result.partial_markdown == "a"
     assert result.errors[0].error_type == "ModifierContractError"
+    assert result.errors[0].stage is ErrorStage.PREFLIGHT
 
 
 def test_metadata_changed_by_proposal_function_fails_before_application() -> None: