feat(06-02): implement JSONFormatter with Unmask support

- Renders findings as 2-space indented JSON array
- Honors Options.Unmask for key field exposure
- Omits empty verify fields via json omitempty
- Registers under "json" in output registry

pkg/output/json.go

@@ -0,0 +1,67 @@
+package output
+
+import (
+	"encoding/json"
+	"io"
+	"time"
+
+	"github.com/salvacybersec/keyhunter/pkg/engine"
+)
+
+func init() {
+	Register("json", JSONFormatter{})
+}
+
+// JSONFormatter renders findings as a JSON array with 2-space indent.
+// Empty input produces "[]\n". When Options.Unmask is false the "key"
+// field carries the masked representation; "key_masked" always carries
+// the masked form regardless of Unmask. Verification fields are omitted
+// when empty so unverified scans stay compact.
+type JSONFormatter struct{}
+
+type jsonFinding struct {
+	Provider       string            `json:"provider"`
+	Key            string            `json:"key"`
+	KeyMasked      string            `json:"key_masked"`
+	Confidence     string            `json:"confidence"`
+	Source         string            `json:"source"`
+	SourceType     string            `json:"source_type"`
+	Line           int               `json:"line"`
+	Offset         int64             `json:"offset"`
+	DetectedAt     string            `json:"detected_at"`
+	Verified       bool              `json:"verified"`
+	VerifyStatus   string            `json:"verify_status,omitempty"`
+	VerifyHTTPCode int               `json:"verify_http_code,omitempty"`
+	VerifyMetadata map[string]string `json:"verify_metadata,omitempty"`
+	VerifyError    string            `json:"verify_error,omitempty"`
+}
+
+// Format implements the Formatter interface.
+func (JSONFormatter) Format(findings []engine.Finding, w io.Writer, opts Options) error {
+	out := make([]jsonFinding, 0, len(findings))
+	for _, f := range findings {
+		key := f.KeyMasked
+		if opts.Unmask {
+			key = f.KeyValue
+		}
+		out = append(out, jsonFinding{
+			Provider:       f.ProviderName,
+			Key:            key,
+			KeyMasked:      f.KeyMasked,
+			Confidence:     f.Confidence,
+			Source:         f.Source,
+			SourceType:     f.SourceType,
+			Line:           f.LineNumber,
+			Offset:         f.Offset,
+			DetectedAt:     f.DetectedAt.Format(time.RFC3339),
+			Verified:       f.Verified,
+			VerifyStatus:   f.VerifyStatus,
+			VerifyHTTPCode: f.VerifyHTTPCode,
+			VerifyMetadata: f.VerifyMetadata,
+			VerifyError:    f.VerifyError,
+		})
+	}
+	enc := json.NewEncoder(w)
+	enc.SetIndent("", "  ")
+	return enc.Encode(out)
+}

pkg/output/json_test.go

@@ -142,8 +142,12 @@ func TestJSONFormatter_Indented(t *testing.T) {
 	if err := (JSONFormatter{}).Format([]engine.Finding{f}, &buf, Options{}); err != nil {
 		t.Fatalf("Format returned error: %v", err)
 	}
-	// Expect 2-space indent on at least one property line.
-	if !strings.Contains(buf.String(), "\n  \"provider\"") {
-		t.Errorf("output not indented with 2 spaces:\n%s", buf.String())
+	// Expect 2-space indent: array items at 2 spaces, nested fields at 4 spaces.
+	s := buf.String()
+	if !strings.Contains(s, "\n  {") {
+		t.Errorf("array item not indented with 2 spaces:\n%s", s)
+	}
+	if !strings.Contains(s, "\n    \"provider\"") {
+		t.Errorf("nested field not indented with 4 spaces:\n%s", s)
 	}
 }