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/truncate_bytes_test.go

@@ -0,0 +1,15 @@
+package parser
+
+import "testing"
+
+func TestTruncateBytes(t *testing.T) {
+	if got := TruncateBytes([]byte("abc"), 3); got != "abc" {
+		t.Fatalf("TruncateBytes() = %q, want %q", got, "abc")
+	}
+	if got := TruncateBytes([]byte("abcd"), 3); got != "abc..." {
+		t.Fatalf("TruncateBytes() = %q, want %q", got, "abc...")
+	}
+	if got := TruncateBytes([]byte("abcd"), -1); got != "" {
+		t.Fatalf("TruncateBytes() = %q, want empty string", got)
+	}
+}