Also export CHECKSUMS from checksum.ts and read expected values from it
in checksum.test.ts so tests don't need updating on every version bump.
Mocks the computed hash via crypto.createHash; expected hash comes from
the module itself. Tests now validate branching/platform dispatch
instead of hardcoded hex values. Added darwin and win32 coverage cases.
Varun Sharma
1b9c34e9f9