docs(packages): document native installs

[jmgilman]

Summary

• document signed APT, DNF, and APK installation and update commands proven against the public origin
• document fail-closed recovery and manual key replacement without verification bypasses
• replace the producer dispatch snippet with the reusable v0.1.16 workflow
• add the package-repository job to the Go example, disabled by default until central onboarding and native signing are complete

Verification

• actionlint examples/go-release/.github/workflows/release.yml
• public APT install of release-cli 0.1.16 in pinned Debian
• public DNF install with metadata and package signature checks in pinned Fedora
• public APK install with aggregate and producer keys in pinned Alpine
• automatic repository dispatch run 32551330487
• unchanged replay run 32551525329