ci: autonomous releases with deferred registry publishing

[zackees]

Summary

Implements #203 following soldr/zccache version-bump automation. Adds auto-release.yml for main Cargo-version bumps and manual dispatch (dry-run by default), reuses existing all-feature package and six-target worker gates, and creates GitHub releases directly without relying on bot-triggered release events.

Crates.io and PyPI remain disabled until repository opt-in variables and credentials are configured by the owner. GitHub assets publish independently. Registry jobs wait for immutable GitHub asset verification; tag dispatch supports later registry recovery. No tokens or repository variables were changed and no release was dispatched.

Validation

• Focused regression RED before implementation, GREEN afterward (5 tests).
• Existing package configuration test and process-substrate validator passed.
• Rust facade-policy tests: 15 passed; strict targeted Clippy and fmt passed.
• actionlint, Ruff, diff whitespace checks passed.
• Single-agent clud-review clean after addressing artifact layout, publication ordering, tag recovery and variable scope.
• Hosted workflow execution remains to be verified; local checks do not constitute a release.

Coordinated with FastLED/cli#242. This release infrastructure must land before the final migration release.