Bucket divisor now produces [0, 1) so the single UUID hashing to
0xFFFFFFFF is no longer permanently excluded by the strict-less-than
admit condition.
Mirrors the post-stamp manifest validation step from desktop-rollout.yml
into desktop-release.yml's finalize-rollout job so a stamp-rollout.mjs
regression can't silently ship a broken manifest.
Adds boundary tests: bucket=0 stays blocked at exact release time,
max-bucket admits at and past rollout end, unparseable releaseDate
admits, bucketFromStagingUserId is strictly < 1 at the upper bound.
Mohamed Boudra
e41fee0366