fix: parser critical bugs and add PR #86 compatibility

Fixes 3 critical bugs in parser.go:

1. Gemini detection: Change Delta from bool to *bool for proper field
   presence detection. Fixes issue where delta:false events were lost.

2. Codex detection: Tighten logic to only classify as Codex if
   thread_id exists OR item.type is non-empty. Prevents Claude events
   with item:null/item:{} from being misclassified and dropped.

3. Performance: Move itemHeader parsing inside item.completed case,
   only parse when actually needed.

Additional changes:
- Implement PR #86's Gemini notifyMessage trigger on Status field
  instead of Content, resolving parser.go conflict between PRs
- Add regression tests for all fixed scenarios
- All tests pass: go test ./...

Co-authored-by: Codeagent (Codex)

Generated with SWE-Agent.ai

Co-Authored-By: SWE-Agent.ai <noreply@swe-agent.ai>

codeagent-wrapper/main_test.go

@@ -1582,6 +1582,34 @@ func TestBackendParseJSONStream_ClaudeEvents(t *testing.T) {
 	}
 }
 
+func TestBackendParseJSONStream_ClaudeEvents_ItemDoesNotForceCodex(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+	}{
+		{
+			name:  "null item",
+			input: `{"type":"result","result":"OK","session_id":"abc123","item":null}`,
+		},
+		{
+			name:  "empty object item",
+			input: `{"type":"result","subtype":"x","result":"OK","session_id":"abc123","item":{}}`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			message, threadID := parseJSONStream(strings.NewReader(tt.input))
+			if message != "OK" {
+				t.Fatalf("message=%q, want %q", message, "OK")
+			}
+			if threadID != "abc123" {
+				t.Fatalf("threadID=%q, want %q", threadID, "abc123")
+			}
+		})
+	}
+}
+
 func TestBackendParseJSONStream_GeminiEvents(t *testing.T) {
 	input := `{"type":"init","session_id":"xyz789"}
 {"type":"message","role":"assistant","content":"Hi","delta":true,"session_id":"xyz789"}
@@ -1598,6 +1626,43 @@ func TestBackendParseJSONStream_GeminiEvents(t *testing.T) {
 	}
 }
 
+func TestBackendParseJSONStream_GeminiEvents_DeltaFalseStillDetected(t *testing.T) {
+	input := `{"type":"init","session_id":"xyz789"}
+{"type":"message","content":"Hi","delta":false,"session_id":"xyz789"}
+{"type":"result","status":"success","session_id":"xyz789"}`
+
+	message, threadID := parseJSONStream(strings.NewReader(input))
+
+	if message != "Hi" {
+		t.Fatalf("message=%q, want %q", message, "Hi")
+	}
+	if threadID != "xyz789" {
+		t.Fatalf("threadID=%q, want %q", threadID, "xyz789")
+	}
+}
+
+func TestBackendParseJSONStream_GeminiEvents_OnMessageTriggeredOnStatus(t *testing.T) {
+	input := `{"type":"init","session_id":"xyz789"}
+{"type":"message","role":"assistant","content":"Hi","delta":true,"session_id":"xyz789"}
+{"type":"message","content":" there","delta":true}
+{"type":"result","status":"success","session_id":"xyz789"}`
+
+	var called int
+	message, threadID := parseJSONStreamInternal(strings.NewReader(input), nil, nil, func() {
+		called++
+	})
+
+	if message != "Hi there" {
+		t.Fatalf("message=%q, want %q", message, "Hi there")
+	}
+	if threadID != "xyz789" {
+		t.Fatalf("threadID=%q, want %q", threadID, "xyz789")
+	}
+	if called != 1 {
+		t.Fatalf("onMessage called=%d, want %d", called, 1)
+	}
+}
+
 func TestBackendParseJSONStreamWithWarn_InvalidLine(t *testing.T) {
 	var warnings []string
 	warnFn := func(msg string) { warnings = append(warnings, msg) }