[workflow-patrol] Workflow drift detected: duplicate-issue-detector missing runtime setup hook

## Findings

### 1. `gh-aw-duplicate-issue-detector.md` is the only public workflow missing the standard runtime setup hook

**Which workflow deviates**
- `.github/workflows/gh-aw-duplicate-issue-detector.md`

**Majority pattern**
- Public workflow sources under `.github/workflows/gh-aw-*.md` consistently include both:
- `gh-aw-fragments/runtime-setup.md` in `imports`
- `setup-commands` in `on.workflow_call.inputs`
- Current counts in this repository: **53/54 workflows (98.1%)** include each of those two elements.

**Examples that follow the majority pattern**
- `.github/workflows/gh-aw-bug-hunter.md:7` and `.github/workflows/gh-aw-bug-hunter.md:35`
- `.github/workflows/gh-aw-pr-review.md:7` and `.github/workflows/gh-aw-pr-review.md:38`
- `.github/workflows/gh-aw-text-auditor.md:7` and `.github/workflows/gh-aw-text-auditor.md:34`

**What is different in the outlier**
- Import block omits runtime setup fragment: `.github/workflows/gh-aw-duplicate-issue-detector.md:4-10`
- Input block omits `setup-commands` (it jumps from `additional-instructions` to `allowed-bot-users`): `.github/workflows/gh-aw-duplicate-issue-detector.md:25-34`
- Peer workflows that include these also include a `Repo-specific setup` step (for example: `.github/workflows/gh-aw-bug-hunter.md:91`, `.github/workflows/gh-aw-pr-review.md:97`, `.github/workflows/gh-aw-text-auditor.md:114`), which this workflow currently cannot support via caller input.

**Suggested fix**
- Add `gh-aw-fragments/runtime-setup.md` to `imports` in `.github/workflows/gh-aw-duplicate-issue-detector.md`.
- Add optional `setup-commands` input under `on.workflow_call.inputs` using the standard description/default used by peer workflows.
- Ensure the corresponding setup step is present so callers can run repo-specific bootstrapping consistently.

## Suggested Actions

- [ ] Add `runtime-setup` import and `setup-commands` input to `gh-aw-duplicate-issue-detector.md` to match the established workflow structure.

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