fix: repair unescaped quotes in LLM JSON responses

LLMs (especially Sonnet) sometimes emit JSON with unescaped double
quotes inside string values, e.g. (e.g. "28") instead of properly
escaping them. This caused parse failures in CI.

Add a repairJSON fallback that uses a character-by-character scanner
to identify interior quotes (those not followed by structural JSON
characters) and escape them before retrying the parse.

Fixes sonnet-review failures on gargoyle PR #551.

review/parser_test.go

@@ -1,6 +1,7 @@
 package review
 
 import (
+	"encoding/json"
 	"testing"
 )
 
@@ -112,3 +113,39 @@ func TestParseResponse_MarkdownFencesNoLang(t *testing.T) {
 		t.Errorf("expected APPROVE, got %q", result.Verdict)
 	}
 }
+
+func TestParseResponse_UnescapedQuotesInStrings(t *testing.T) {
+	// Real failure from CI: Sonnet puts unescaped quotes like (e.g. "28") in findings
+	input := `{"verdict": "APPROVE", "summary": "Clean PR", "findings": [{"severity": "NIT", "file": "ci/Dockerfile", "line": 14, "finding": "The comment says OTP_VERSION is the major version (e.g. \"28\") but it actually contains unescaped quotes like (e.g. "28") which breaks JSON"}], "recommendation": "Ship it"}`
+
+	result, err := ParseResponse(input)
+	if err != nil {
+		t.Fatalf("expected repair to handle unescaped quotes, got error: %v", err)
+	}
+	if result.Verdict != "APPROVE" {
+		t.Errorf("expected APPROVE, got %q", result.Verdict)
+	}
+	if len(result.Findings) != 1 {
+		t.Fatalf("expected 1 finding, got %d", len(result.Findings))
+	}
+}
+
+func TestRepairJSON_NoOpOnValid(t *testing.T) {
+	valid := `{"key": "value", "num": 42}`
+	result := repairJSON(valid)
+	if result != valid {
+		t.Errorf("repairJSON should not modify valid JSON\n  got:  %s\n  want: %s", result, valid)
+	}
+}
+
+func TestRepairJSON_FixesUnescapedQuotes(t *testing.T) {
+	// Interior quote followed by non-structural character
+	input := `{"msg": "use "foo" here"}`
+	result := repairJSON(input)
+
+	// Should be parseable now
+	var m map[string]interface{}
+	if err := json.Unmarshal([]byte(result), &m); err != nil {
+		t.Fatalf("repaired JSON should parse, got: %v\nrepaired: %s", err, result)
+	}
+}