fix: resolve VSIX glob path before publishing extension

[jrandolf]

Summary

• Add a "Find VSIX file" step to resolve the actual .vsix filename before passing it to HaaLeo/publish-vscode-extension
• The action does not support glob patterns in extensionFile, causing ENOENT: no such file or directory, open 'dist/*.vsix'

Test plan

• Merge and retag v0.1.7 to verify the publish jobs succeed