Add correction proposal models

internal/framework/proposals/proposal.go

@@ -0,0 +1,49 @@
+package proposals
+
+import (
+	"fmt"
+	"strings"
+)
+
+// CorrectionProposal is the base proposal emitted by correction modules.
+type CorrectionProposal struct {
+	TargetSegmentID int     `json:"id"`
+	OriginalText    string  `json:"original_text"`
+	CorrectedText   string  `json:"corrected_text"`
+	Confidence      float64 `json:"confidence"`
+}
+
+// ProposalMetadata is framework-enriched execution metadata for a proposal.
+type ProposalMetadata struct {
+	ProposalIndex  int    `json:"proposal_index"`
+	ModuleKey      string `json:"module_key"`
+	ModuleInstance string `json:"module_instance"`
+	SectionIndex   *int   `json:"section_index,omitempty"`
+}
+
+// EnrichedCorrectionProposal combines module-emitted proposal data with
+// framework execution metadata.
+type EnrichedCorrectionProposal struct {
+	CorrectionProposal
+	ProposalMetadata
+}
+
+// Validate checks only basic structural integrity of the proposal.
+// Semantic checks (staleness, span presence, replacement behavior) are handled
+// by later proposal preview/application and validator phases.
+func (p CorrectionProposal) Validate() error {
+	if p.TargetSegmentID <= 0 {
+		return fmt.Errorf("proposal id must be positive")
+	}
+	if strings.TrimSpace(p.OriginalText) == "" {
+		return fmt.Errorf("proposal original_text must not be empty")
+	}
+	if strings.TrimSpace(p.CorrectedText) == "" {
+		return fmt.Errorf("proposal corrected_text must not be empty")
+	}
+	if p.Confidence < 0.0 || p.Confidence > 1.0 {
+		return fmt.Errorf("proposal confidence must be between 0.0 and 1.0")
+	}
+
+	return nil
+}