release workflow: fix mathjax.tar path, add manual retry trigger

[jmnote]

Summary

The v1.0.1 release run (triggered by #77) failed at the "Create GitHub release" step: https://github.com/jmnote/SimpleMathJax/actions/runs/34053829578

tar: mathjax.tar: Cannot open: No such file or directory
tar: Exiting with failure status due to previous errors
##[error]Process completed with exit code 2.

git archive ... -o ../mathjax.tar ran from inside a ( cd resources/MathJax && ... ) subshell, so ../mathjax.tar resolved to resources/mathjax.tar, not the repo root where the following tar -Af base.tar mathjax.tar looked for it. Fixed by writing both archives to an absolute path captured before the cd.

Since extension.json's version (1.0.1) didn't change again after that failed run, the push-triggered "version changed" check would skip re-running the release step even after this fix merges. Added a workflow_dispatch trigger so the release can be retried by hand — github.event.before is empty on a manual run, so the version-changed check always treats it as changed, and the existing gh release view guard still skips it if that tag's release already exists.

Testing

• Reproduced the fix against a detached worktree of main: SimpleMathJax-1.0.1-with-mathjax.tar.gz (6.2M) now builds successfully and contains resources/MathJax/tex-chtml.js and extension.json at the expected paths.
• Validated the workflow YAML parses.

Follow-up

After this merges, the v1.0.1 release needs to be triggered manually (gh workflow run release.yml or the Actions tab's "Run workflow" button), since the version didn't change again in this PR.

🤖 Generated with Claude Code

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