fix(webapp): guard workload auth gate metric against dev HMR re-registration

[kathiekiwi]

Wraps the workload_auth_gate_total Counter in the singleton helper (same pattern as reloadingRegistry.server.ts) so a dev hot reload doesn't crash with "A metric with the name workload_auth_gate_total has already been registered". No production behavior change.

[changeset-bot]

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Latest commit: 6017944

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[coderabbitai]

Walkthrough

The worker group token service now registers workloadAuthGateCounter through singleton(...) rather than direct module-load instantiation. The counter’s metric name, help text, label names, and metricsRegister binding remain unchanged.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description states the change and rationale, but it omits required template sections like Closes #issue, checklist, testing, changelog, and screenshots.	Add the missing template sections, include the issue reference, and briefly document testing, changelog, and screenshots if applicable.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly describes the main change: preventing dev HMR metric re-registration.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/workload-auth-gate-metric-hmr

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.