feat: add floating tag maintenance workflow

[rozsazoltan]

Summary

Adds an explicit floating tag maintenance flow for the unified toolchain release model.

The normal release flow still updates floating tags during github-release finalize, but the repository now also has a dedicated workflow that can repair or recalculate moving tags after manual tag changes.

Changes

• Add github-release update-floating-tags as a clear command alias for floating tag synchronization.
• Restore a focused Update Floating Tags workflow.
• Run floating tag maintenance automatically when version tags are pushed or deleted.
• Support manual workflow dispatch for:
  • all release tags
  • a specific semantic version
  • a specific tag
• Keep floating tag updates out of release asset builds.
• Update repository checks to require the maintenance workflow.

Notes

This is useful when tags such as vX, vX.Y, latest, or next need to be recalculated after a versioned vX.Y.Z tag is added, deleted, or manually changed.