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/.gitignore

@@ -1,4 +1,7 @@
 # Build artifacts
+bin/
+codeagent
+codeagent.exe
 codeagent-wrapper
 codeagent-wrapper.exe
 *.test
@@ -9,3 +12,12 @@ coverage*.out
 cover.out
 cover_*.out
 coverage.html
+
+# Logs
+*.log
+
+# Temp files
+*.tmp
+*.swp
+*~
+.DS_Store