fix(system): propagate command-check and version parse fixes to v0.40-dev

[MuncleUscles]

Propagates the stable fix merged in #349 to the next dev line.

Includes:

• command checks now fail closed on any rejected exec
• version parsing now throws on empty or non-matching stdout
• regression tests for ENOENT, no-stderr command failures, and non-matching version output

Verification on this branch:

• npm run test -- tests/libs/system.test.ts
• npm run build

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