workflows/hetzner: expose machine_count and server_type as dispatch inputs

[igorpecovnik]

Summary

The Hetzner runner workflow advertised four knobs (MACHINE, MACHINE_COUNT, RUNNER_COUNT, PERIOD) in its original commit message but none were actually wired up — workflow_dispatch had no inputs: block, so ${{ env.MACHINE || 'cax41' }} and ${{ env.MACHINE_COUNT || '4' }} always evaluated to the default and the workflow name ("Enable 16 Hetzner ARM64 runners") was literally the only thing it could do.

First pass at making it configurable:

• machine_count — choice of 1/2/4/8/16, default 4. Matrix generator now reads inputs.machine_count.
• server_type — choice of cax41/cax31/cax21, default cax41. Create and Cleaning both pick it up. The action auto-falls back to a smaller type on capacity shortage, so this is "biggest you're willing to wait for".

|| '<default>' fallbacks are kept so repository_dispatch / REST API callers that omit inputs keep working as before.

Workflow renamed to drop the "16" — it's now variable.

Out of scope (follow-ups)

• RUNNER_COUNT and PERIOD are still hardcoded; wiring those is a separate pass.
• The "Hetzner VMs come up but runners don't register" issue we hit last run — needs an actual armbian-config / HETZNER_RUNNER token investigation; not a workflow-shape problem.

Test plan

• Trigger via UI with all defaults → 4 × cax41 as before
• Trigger via UI with machine_count=2, server_type=cax31 → 2 × cax31
• Trigger via REST API without any inputs → falls back to 4 × cax41 (verifies the `|| ''` path)

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 5c6fd792-26ba-4de5-8d35-443268871318

📥 Commits

Reviewing files that changed from the base of the PR and between 2c42287 and 9ffdd18.

📒 Files selected for processing (1)

• .github/workflows/infrastructure-hetzner-runners.yml

Walkthrough

The workflow now accepts configurable inputs via manual dispatch: machine_count and server_type parameters with specified defaults and constrained option lists. The matrix generation step is updated to use the dispatch input machine_count (defaulting to 4) instead of a hardcoded environment variable. The Hetzner runner provisioning and cleanup steps are modified to derive server_type from the dispatch input instead of a static environment variable (defaulting to cax41). The workflow name is also updated to remove hardcoded "16" wording. Changes total +29/-4 lines across a single workflow file.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: exposing machine_count and server_type as configurable dispatch inputs in the Hetzner workflow.
Description check	✅ Passed	The description clearly explains the purpose of the changes, the inputs being added, backward compatibility measures, scope limitations, and a test plan.
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.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch hetzner-workflow-dispatch-inputs

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