ci: add release creation workflow

[David Pine (IEvangelist)]

Summary

• Add a release creation workflow for merged sync PRs into main.
• Read the release version from .plugin/plugin.json, create the corresponding v{version} GitHub release, and extract matching notes from CHANGELOG.md with a fallback.
• Pin actions/checkout to the latest release SHA with a version comment.
• Reset plugin, marketplace, Gemini, and top-level skill version metadata to 0.0.1.
• Update the changelog header so the workflow resolves v0.0.1 with real notes.
• Expand plugin and marketplace keywords/tags beyond .NET to include TypeScript, JavaScript, Python, and AppHost scenarios.
• Validation: confirmed required files exist, simulated version/tag and release-note extraction locally, parsed updated JSON manifests, and checked workflow/metadata diffs with git diff --check.