Publish SDK releases to GitHub Packages and remove completed plan

[roncodes]

Summary

• Publish every completed SDK release to GitHub Packages as well as npm. The GitHub release already existed, but the previous workflow did not include a GitHub Packages publication job.
• Use the repository's GITHUB_TOKEN with packages: write, matching the other modules' GitHub registry authentication. npm continues to use NPM_AUTH_TOKEN.
• Download the exact GitHub release tarball, validate its package/repository/version/checksum, and compare it with the published npm bytes before mirroring. Do not rebuild or modify the package.
• Verify the package downloaded from GitHub Packages byte-for-byte. Retry identical versions safely; refuse conflicts and fail on authorization errors.
• Add a GitHub-Packages-only manual recovery mode for existing releases, including v2.0.0. This mode never tags, rebuilds, or publishes to npm, and requires the existing release tag to belong to main.
• Remove the obsolete MODERNIZATION_PLAN.md as requested, and replace its README link with the release guide. The deleted plan remains recoverable from Git history.

Verification

• Full local verification passes: formatting, lint, types, 11 release automation tests, 34 SDK tests, 100% statements/branches/functions/lines, build, package/type/export validation.
• Release tests cover artifact identity, checksums, prereleases, safe retries, conflicting bytes, authorization failures, downloaded package integrity, and local publication guards.
• Workflow syntax validation passes.
• No SDK API changes and no version bump; the existing v2.0.0 tag and npm publication are not changed.

Release recovery

The authorized v2.0.0 recovery completed successfully in run 34448027375, using version=2.0.0 and github_packages_only=true from this fix branch.

• @fleetbase/sdk@2.0.0 is published at GitHub Packages, with public visibility and repository association fleetbase/fleetbase-js.
• The downloaded GitHub package was verified byte-for-byte against both the existing npm publication and GitHub release asset.
• The tag/npm/GitHub-release job was skipped. Existing npm bytes and the v2.0.0 tag were not changed.

Automatic GitHub Packages publication for future releases becomes active when this PR merges. This PR itself is not a release branch and merging it will not publish a new npm version.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (8d1ead1) to head (718a7f6).

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #40   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           17        17           
  Lines          866       866           
  Branches       144       144           
=========================================
  Hits           866       866           

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