[jlongster]

• Removes the check-duplicates job from pr-management.yml; only add-contributor-label remains.
• script/duplicate-pr.ts has been entirely commented out since the npm-scope migration (refactor(packages): migrate to the opencode npm scope #47852), so the job printed nothing and posted an empty "The following comment was made by an LLM, it may be inaccurate:" comment on every outside PR (e.g. docs: improve contributing guidelines and environment verification #57566, docs: add security review documentation #57369, fix(install): normalize Windows TMPDIR in the curl installer #57355).
• It also ran on outsiders' PRs (pull_request_target) with OPENCODE_API_KEY and GITHUB_TOKEN in its environment; removing it takes the key out of that path. The GitHub triage bot already checks outside PRs for duplicates.
• Deletes the dead script/duplicate-pr.ts and its .opencode/agent/duplicate-pr.md agent.

[opencode-agent]

I found no problems with this change. It's CI-only, so there was nothing to run; I checked that the trimmed workflow still parses with only add-contributor-label, that script/duplicate-pr.ts really was all commented out on the base (so the job could only post an empty comment), and that nothing else references the deleted agent or script. Dropping the issue-event branch from the label script is safe because the workflow only triggers on pull_request_target.

Public API: unchanged.

One small leftover: .opencode/tool/github-pr-search.ts is now used by nothing. It's turned off globally in .opencode/opencode.jsonc, and the deleted agent was its only user, so it could be removed separately if it's no longer needed.