feat(cpp): gaia-bash — native C++ bash coding agent with TUI, API server, MCP server #200

Job	Run time
C++ (ubuntu-latest)	5m 23s
C++ (windows-latest)	17m 55s
C++ Integration Tests (STX)	2m 19s
C++ Shared Library (windows-latest)	12m 40s
C++ Install Test (windows-latest)	14m 22s
C++ Install Test (ubuntu-latest)	3m 5s
C++ Shared Library (ubuntu-latest)	4m 0s
C++ Build Summary	2s
C++ Benchmarks	0s
	59m 46s

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