Make module-stage LLM handling resilient and report warnings

internal/framework/proposals/preview_test.go

@@ -121,6 +121,42 @@ func TestPreviewProposalForSegmentNoEffectReplacement(t *testing.T) {
 	}
 }
 
+func TestPreviewProposalForSegmentAllowsEmptyCorrectedTextWhenSegmentRemainsNonEmpty(t *testing.T) {
+	segment := &schema.Segment{ID: 8, Text: "uh hello"}
+	proposal := CorrectionProposal{
+		TargetSegmentID: 8,
+		OriginalText:    "uh ",
+		CorrectedText:   "",
+		Confidence:      0.9,
+	}
+
+	result := PreviewProposalForSegment(segment, proposal, ReplacementPolicyRequireUnique)
+	if !result.Applicable {
+		t.Fatalf("expected applicable preview, got skip reason %q", result.SkipReason)
+	}
+	if result.CorrectedSegmentText != "hello" {
+		t.Fatalf("unexpected corrected text: %q", result.CorrectedSegmentText)
+	}
+}
+
+func TestPreviewProposalForSegmentRejectsEmptyResultingSegment(t *testing.T) {
+	segment := &schema.Segment{ID: 8, Text: "uh"}
+	proposal := CorrectionProposal{
+		TargetSegmentID: 8,
+		OriginalText:    "uh",
+		CorrectedText:   "",
+		Confidence:      0.9,
+	}
+
+	result := PreviewProposalForSegment(segment, proposal, ReplacementPolicyRequireUnique)
+	if result.Applicable {
+		t.Fatal("expected non-applicable preview")
+	}
+	if result.SkipReason != SkipReasonEmptyResultingText {
+		t.Fatalf("expected skip reason %q, got %q", SkipReasonEmptyResultingText, result.SkipReason)
+	}
+}
+
 func TestPreviewProposalForSegmentPreservesInputSegment(t *testing.T) {
 	segment := &schema.Segment{ID: 9, Speaker: "A", Start: 1.0, End: 2.0, Text: "rank rank"}
 	original := *segment