test: add compiler, COFF, CLI coverage and CI workflow

[wr0belj]

Adds layered test coverage for shellcode generation, COFF output, CLI behavior, negative compiler cases, debug maps, parser/codegen units, and OPSEC determinism.

[github-actions]

Test summary

Suite	Command	Result
entropykit unit tests	cargo test -p entropykit --bin entc	PASS
shellcode goldens	cargo test -p entropykit --test shellcode_golden	PASS
COFF smoke tests	cargo test -p entropykit --test coff_smoke	PASS
CLI smoke tests	cargo test -p entropykit --test cli_smoke	PASS
negative compiler tests	cargo test -p entropykit --test typecheck_negative	PASS
debug map golden	cargo test -p entropykit --test debug_map_golden	PASS
BOF loader tests	cargo test -p bof-loader	PASS
remaining workspace crates	cargo test --workspace --exclude entropykit --exclude bof-loader	PASS

Result: all test suites passed.