Fix "sushi" CI job by avoiding self-overwrite corruption in _updatePublisher.sh

[Copilot]

The sushi validate job (check run 100633579979) was failing at sudo nvm install 22 since nvm is a shell function, not a system command, and can't be invoked via sudo.

Findings

• The reported nvm failure was already fixed on top of this branch by a prior commit switching to sudo npm install -g fsh-sushi.
• Tracing later CI runs showed the same sushi job still failing, now in the "Update publisher" step, with garbled errors like line 145: i: command not found.
• Root cause: _updatePublisher.sh downloads a fresh copy of itself and overwrites its own file in place while bash is still executing it, corrupting bash's read buffer mid-script. Reproduced this exact corruption pattern locally with a minimal self-modifying script repro.

Fix

• Run the script from a copied path so the file bash actively reads is never the one being overwritten, while it still updates ./_updatePublisher.sh in the working directory as intended:

- name: Update publisher
  run: cp _updatePublisher.sh /tmp/_updatePublisher.sh && bash /tmp/_updatePublisher.sh -f -y