Add explicit token inputs to the checkout and softprops/action-gh-release
steps so the GitHub token is wired through instead of relying on implicit
defaults. The workflow-level contents: write permission already scopes
the token correctly for tag/release creation.
Pushing a tag matching v* (or running the workflow manually with an
existing tag) cross-compiles the four supported targets via
`make build-all`, generates a SHA256SUMS file, and publishes a GitHub
release with all binaries attached.
Claude