refactor: clean up main.rs by removing unused imports and simplifying… #163

Job	Run time
prepare	5s
build-ubuntu	10m 22s
build-macos (--target aarch64-apple-darwin, silicon)	6h 0m 2s
build-macos (--target x86_64-apple-darwin, intel)	6h 0m 1s
build-windows (--target x86_64-pc-windows-msvc, x64, x86_64-pc-windows-msvc)	17m 34s
build-windows (--target aarch64-pc-windows-msvc, arm64, aarch64-pc-windows-msvc)	16m 38s
	12h 44m 42s

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