feat: /translate PR comment command + exclude root QMD from format check

[Copilot]

Two workflow improvements: the auto-translate workflow was only triggerable manually or on push/PR open; root-level site navigation QMDs (index.qmd, About.qmd, etc.) were incorrectly flagged by the tutorial format checker.

/translate PR comment command (translate-command.yml — new)

Split the comment-command handling into a dedicated zero-checkout gatekeeper workflow to avoid the issue_comment + untrusted-code-checkout security pattern (CodeQL actions/untrusted-checkout-toctou).

/translate                          # translate all changed QMD files in the PR
/translate Omics/VolcanoPlot.qmd    # target a specific file
/translate File1.qmd File2.qmd      # target multiple files

• Only write/maintain/admin collaborators can trigger; non-collaborators get an error comment + 👎
• Reacts with 👀 on receipt; posts acknowledgement comment with link to workflow runs
• Dispatches auto-translate.yml via workflow_dispatch with pr_number + optional files inputs — no checkout, no code execution in this workflow

auto-translate.yml — updated

• Removed issue_comment trigger (now owned by translate-command.yml)
• Added files workflow_dispatch input for file-level targeting (used by the command handler or direct manual dispatch)
• PR translation-summary comment now also fires when dispatched via workflow_dispatch with a pr_number

pr-review.yml — format check scope fix

Added f.filename.includes('/') to the QMD filter so root-level files are excluded from tutorial format validation.

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[github-actions]

✅ QMD Format Check

No new QMD tutorial files to check.

Automated check by the PR Review workflow.
See contribution guidance for the expected tutorial format.