chore: [#1397] skip chore label for Dependabot PRs in pr-labeler (#1398)

## Summary
- Dependabot PRs were getting a `chore` label because their titles start
with `chore(deps):`, triggering the pr-labeler workflow
- Added an early return in `pr-labeler.yml` to skip labeling when the PR
author is `dependabot[bot]`
- Dependabot PRs already get the `dependencies` label via
`dependabot.yml` — no change needed there

closes #1397

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Co-authored-by: milkyskies <milkyskies>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: milkyskies

.github/workflows/pr-labeler.yml

@@ -14,6 +14,8 @@ jobs:
         uses: actions/github-script@v9
         with:
           script: |
+            if (context.payload.pull_request.user.login === 'dependabot[bot]') return;
+
             const title = context.payload.pull_request.title;
             const labels = [];