Switch NuGet publish workflow to tag-driven releases with 4-part versioning

[Copilot]

This updates the release pipeline to publish from version tags instead of release events. Tags like v9.3.0.4 now drive package version generation, package builds, GitHub Release publication, GitHub Packages publication, and NuGet.org publication in one flow.

• Tag-driven release entrypoint

  • Replace release.published trigger with push.tags: v*
  • Keep workflow_dispatch for manual runs, but align its version input with the same tag-based format

• Version normalization

  • Add a dedicated prepare job to derive the package version from the tag/input
  • Strip the v prefix for dotnet pack
  • Enforce the repository’s 4-part version format: v9.3.0.4 / 9.3.0.4

• Packaging flow

  • Reuse the normalized version across all package builds:
    • LVGLSharp.Native
    • LVGLSharp.Interop
    • LVGLSharp.Core
    • LVGLSharp.Runtime.Windows
    • LVGLSharp.Runtime.Linux
    • LVGLSharp.Forms
  • Preserve the existing native artifact + local NuGet source flow

• Release publishing

  • On tag builds, publish .nupkg artifacts to:
    • GitHub Release
    • GitHub Packages
    • NuGet.org
  • Handle reruns safely by uploading to an existing GitHub Release when present, or creating it when missing

• Workflow hardening

  • Add explicit minimal permissions for the new prepare job
  • Improve release lookup failure reporting for non-404 GitHub API responses

on:
  push:
    tags:
      - "v*"

# v9.3.0.4 -> 9.3.0.4
VERSION="${RAW_VERSION#v}"

dotnet pack ... -p:Version=${{ needs.prepare.outputs.package_version }}

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[Copilot]

Pull request overview

This PR updates the NuGet publishing workflow to run from version tags (e.g., v9.3.0.4) instead of release.published, and introduces a dedicated version normalization/validation step to enforce 4-part versions across all packaged projects.

Changes:

• Switch workflow trigger from release.published to push.tags: v* (while keeping workflow_dispatch).
• Add a prepare job to normalize and validate the version (strip leading v, enforce x.y.z.w) and expose it via job outputs.
• Use the normalized version output for all dotnet pack steps, and add GitHub Release upload/create behavior on tag builds.