ranade-oss makes production releases test reality, not permissions metadata

The fork now checks whether its release process can actually write to the repository by safely simulating the creation of a release marker, rather than trusting a permissions readout that proved inaccurate.

That matters because a recent release had already cleared quality checks, deployment rehearsal, rollback verification and legal-source checks before being blocked by that misleading signal. The new check still halts a release if the repository rejects the simulated write or if the temporary marker conflicts with an existing one. It also cleans up after itself whether the check passes or fails.