fix(ci): push detached HEAD to history ref and drop worktree cleanup

[stasadev]

The Issue

https://github.com/ddev/addon-registry/actions/runs/26116848062/job/76808231099

Preparing worktree (detached HEAD ba7fdb2)
HEAD is now at ba7fdb2 chore(add-ons): snapshot 2026-05-19
[detached HEAD 87932d2] chore(add-ons): snapshot 2026-05-19
 Date: Tue May 19 00:55:31 2026 +0000
 21 files changed, 297 insertions(+), 144 deletions(-)
 create mode 100644 _addons/e0ipso/ddev-assistant-opencode.md
error: src refspec history does not match any
error: failed to push some refs to 'https://github.com/ddev/addon-registry'

How This PR Solves The Issue

• Push via HEAD:history so the push works from a detached HEAD worktree
• Remove the git worktree remove call: the runner discards /tmp anyway

Manual Testing Instructions

Automated Testing Overview

Release/Deployment Notes