feat(matrix-stack): add priorityClassName support to component workloads

[somaz94]

Adds an optional priorityClassName value to every matrix-stack component workload, mirroring the existing nodeSelector pattern. Default is unset so rendered output is unchanged for existing users. Resolves #1422.

Validation (run locally against the repo's own tooling):

• helm lint clean; helm template renders priorityClassName when set, byte-identical to main when unset
• Full pytest tests/manifests passes (2377 passed), including a new test_pod_priorityClassName.py mirroring test_pod_nodeSelector.py
• reuse lint compliant, ruff clean, the assemble scripts reproduce with no drift

This is a per-component knob (like nodeSelector). If you'd prefer a global default with per-component overrides (like tolerations/topologySpreadConstraints), happy to switch.

[github-actions]

dyff of changes in rendered templates of CI manifests

No changes in rendered templates

[benbz]

Hi, thanks for this. It looks basically perfect. Ideally we would like a global priorityClassName, that's default unset (to avoid changes to existing deploys as you've done for the per-component values) but can be used if people want to change the priorityClassName for everything at once.

To document: all Synapse workers use the same priorityClassName as the main process. I'm not requesting that as a change, I think that's fine for now and we can add per-worker support later if needed.

[CLAassistant]

All committers have signed the CLA.

[somaz94]

Thanks @benbz! Added a global priorityClassName (default unset, so existing deploys are unaffected) that all components fall back to, with a per-component value overriding it. Also documented that Synapse workers inherit the main process's priorityClassName. Ready for another look.

[somaz94]

Done — updated the copyright header to # Copyright 2026 Element Creations Ltd. Thanks @benbz!

[benbz]

Done — updated the copyright header to # Copyright 2026 Element Creations Ltd. Thanks @benbz!

As per the suggestion the New Vector Ltd copyright line needed to go too, not just changing the date on the Element Creations Ltd line

[somaz94]

Done — dropped the New Vector Ltd copyright line, the header on the new test file is now just # Copyright 2026 Element Creations Ltd. Thanks!

[benbz]

Thank you very much for your contribution!