refactor: restructure codebase to internal/ directory with modular architecture

- Move all source files to internal/{app,backend,config,executor,logger,parser,utils}
- Integrate third-party libraries: zerolog, goccy/go-json, gopsutil, cobra/viper
- Add comprehensive unit tests for utils package (94.3% coverage)
- Add performance benchmarks for string operations
- Fix error display: cleanup warnings no longer pollute Recent Errors
- Add GitHub Actions CI workflow
- Add Makefile for build automation
- Add README documentation

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

codeagent-wrapper/internal/parser/event.go

@@ -0,0 +1,74 @@
+package parser
+
+import "github.com/goccy/go-json"
+
+// JSONEvent represents a Codex JSON output event.
+type JSONEvent struct {
+	Type     string     `json:"type"`
+	ThreadID string     `json:"thread_id,omitempty"`
+	Item     *EventItem `json:"item,omitempty"`
+}
+
+// EventItem represents the item field in a JSON event.
+type EventItem struct {
+	Type string      `json:"type"`
+	Text interface{} `json:"text"`
+}
+
+// ClaudeEvent for Claude stream-json format.
+type ClaudeEvent struct {
+	Type      string `json:"type"`
+	Subtype   string `json:"subtype,omitempty"`
+	SessionID string `json:"session_id,omitempty"`
+	Result    string `json:"result,omitempty"`
+}
+
+// GeminiEvent for Gemini stream-json format.
+type GeminiEvent struct {
+	Type      string `json:"type"`
+	SessionID string `json:"session_id,omitempty"`
+	Role      string `json:"role,omitempty"`
+	Content   string `json:"content,omitempty"`
+	Delta     bool   `json:"delta,omitempty"`
+	Status    string `json:"status,omitempty"`
+}
+
+// UnifiedEvent combines all backend event formats into a single structure
+// to avoid multiple JSON unmarshal operations per event.
+type UnifiedEvent struct {
+	// Common fields
+	Type string `json:"type"`
+
+	// Codex-specific fields
+	ThreadID string          `json:"thread_id,omitempty"`
+	Item     json.RawMessage `json:"item,omitempty"` // Lazy parse
+
+	// Claude-specific fields
+	Subtype   string `json:"subtype,omitempty"`
+	SessionID string `json:"session_id,omitempty"`
+	Result    string `json:"result,omitempty"`
+
+	// Gemini-specific fields
+	Role    string `json:"role,omitempty"`
+	Content string `json:"content,omitempty"`
+	Delta   *bool  `json:"delta,omitempty"`
+	Status  string `json:"status,omitempty"`
+
+	// Opencode-specific fields (camelCase sessionID)
+	OpencodeSessionID string          `json:"sessionID,omitempty"`
+	Part              json.RawMessage `json:"part,omitempty"`
+}
+
+// OpencodePart represents the part field in opencode events.
+type OpencodePart struct {
+	Type      string `json:"type"`
+	Text      string `json:"text,omitempty"`
+	Reason    string `json:"reason,omitempty"`
+	SessionID string `json:"sessionID,omitempty"`
+}
+
+// ItemContent represents the parsed item.text field for Codex events.
+type ItemContent struct {
+	Type string      `json:"type"`
+	Text interface{} `json:"text"`
+}