feat(release): support multiple binaries per repo in release.yml #40

Generalize the reusable release workflow so one repo can ship more than one binary. packaging/identity.yml gains a binaries: list where each entry carries binary name, archive template, Homebrew canonical cask and aliases, winget id, Chocolatey id, Linux package name, signing identifier, and keychain probe. A single top-level binary: stays valid and is treated as a one-element list. Homebrew, Chocolatey, winget, signing, and darwin-gate jobs run per binary. First consumer: open-cli-collective/google-cli (gro + grw).

Gate: test-actions.yml green; google-readonly's existing identity.yml still validates unchanged.