Moves gordon releases to ermite.
- GoReleaser publishes drafts on git.bnema.dev (templated github_urls); release.yml is skipped on github.com and reads the Go version from go.mod.
- install.sh: stable latest via the forge redirect, prereleases via the forge REST API (single-line JSON parsing), downloads + checksums from the forge. The next channel keeps GitHub (commits/next + codeload).
- setup-gordon action: latest + downloads from the forge; uses url_effective (redirect_url is empty with -L).
- Docs, wiki and Makefile hints point to git.bnema.dev release URLs.
Checks: shellcheck, sh tests/install_next_test.sh (21 passed), goreleaser check, live redirect/REST parsing against neferbar's release.
Note: until the first ermite release of gordon exists, install.sh latest fails (no release on the forge). Cut a release right after merging.