fix(parser): 修复 Gemini init 事件 session_id 未提取的问题 (#111)

Gemini CLI 的 session_id 出现在 init 事件中，但 parser 的 isGemini
判定条件只检查 role/delta/status 字段，导致 init 事件被当作
"Unknown event" 忽略，session_id 无法提取。

修复方案：在 isGemini 条件中增加对 init 事件的识别。

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>

codeagent-wrapper/main_test.go

@@ -2096,6 +2096,16 @@ func TestBackendParseJSONStream_GeminiEvents(t *testing.T) {
 	}
 }
 
+func TestBackendParseJSONStream_GeminiInitEventSessionID(t *testing.T) {
+	input := `{"type":"init","session_id":"gemini-abc123"}`
+
+	_, threadID := parseJSONStream(strings.NewReader(input))
+
+	if threadID != "gemini-abc123" {
+		t.Fatalf("threadID=%q, want %q", threadID, "gemini-abc123")
+	}
+}
+
 func TestBackendParseJSONStream_GeminiEvents_DeltaFalseStillDetected(t *testing.T) {
 	input := `{"type":"init","session_id":"xyz789"}
 {"type":"message","content":"Hi","delta":false,"session_id":"xyz789"}

codeagent-wrapper/parser.go

@@ -171,7 +171,7 @@ func parseJSONStreamInternal(r io.Reader, warnFn func(string), infoFn func(strin
 		if !isClaude && event.Type == "result" && event.SessionID != "" && event.Status == "" {
 			isClaude = true
 		}
-		isGemini := event.Role != "" || event.Delta != nil || event.Status != ""
+		isGemini := (event.Type == "init" && event.SessionID != "") || event.Role != "" || event.Delta != nil || event.Status != ""
 
 		// Handle Codex events
 		if isCodex {