Feature request: Enable `@`/`/` completion when reading queued prompts

[Gleek]

agent-shell-queue-request reads its prompt via read-string, so the minibuffer has none of the agent-shell-completion-mode hooks. @ and / don't complete in the queue path the way they do at the shell prompt.

Proposal

Install the existing CAPFs in the minibuffer for the duration of the read, sourcing data from the originating shell buffer via a buffer-local override. Wrap read-string with minibuffer-with-setup-hook; clean up on minibuffer-exit-hook.

I've this implemented locally and it seems to work well! Can share a PR if you find this useful.

Checklist

• I agree to communicate with the author myself (not AI-generated).
• I've read the README's Filing issues section.
• I'm running the latest versions (fill in below).
  • agent-shell version: main
  • acp.el version: 0.11.2
  • ACP package (e.g. claude-agent-acp) version: claude-agent-acp 0.31.4
  • Agent CLI (e.g. claude, gemini) version: claude 2.1.123
• For requesting new agent support, I'm including a link to the ACP-capable agent or related ACP package.
• For issues, I'm including ACP traffic (as per README).