Hardened the proposal modules to skip malformed proposals rather than hard failing the entire run

internal/framework/contracts/contracts.go

@@ -101,6 +101,7 @@ type ProposalRequest struct {
 	RunSpec      ModuleRunSpec       `json:"run_spec"`
 	LLMClient    StructuredLLMClient `json:"-"`
 	LLMScheduler LLMScheduler        `json:"-"`
+	OnDroppedCandidate func(index int, targetSegmentID int, originalText string, correctedText string, confidence float64, reasonCode string, message string) `json:"-"`
 }
 
 // ValidationRequest is the input to validator execution.