Cancel outdated CI runs when a PR is updated

[rtibbles]

Summary

• Adds concurrency to the nine push/PR-triggered CI workflows
• New commits on a PR cancel in-progress runs for the same head ref
• Group key falls back to github.run_id when github.head_ref is empty, so non-PR runs (pushes to develop/release-v**, the morango_integration cron) never collide
• Skips the asset-comment workflow on cancelled parent builds (still runs on failures)

References

• GitHub Actions concurrency syntax
• Cancelled asset build run from a previous SHA on this PR — proof the cancellation fires on push

Reviewer guidance

• Check the head_ref || run_id fallback — wrong group key would cancel develop/release pushes
• This PR exercises the change: a follow-up push should cancel the previous run

AI usage

Used Claude Code (Opus 4.7) to survey the workflow files, decide which to update, and apply the same concurrency block to all nine. I reviewed and edited the body section by section.

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.19.4a0.dev0_git.18.g1214736f.pex
Windows Installer (EXE)	kolibri-0.19.4a0.dev0+git.18.g1214736f-windows-setup-unsigned.exe
Debian Package	kolibri_0.19.4a0.dev0+git.18.g1214736f-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.19.4a0.dev0+git.18.g1214736f.dmg
Android Package (APK)	kolibri-0.19.4a0.dev0+git.18.g1214736f-0.1.10-debug.apk
Raspberry Pi Image	kolibri-pi-image-0.19.4a0.dev0+git.18.g1214736f.zip
TAR file	kolibri-0.19.4a0.dev0+git.18.g1214736f.tar.gz
WHL file	kolibri-0.19.4a0.dev0+git.18.g1214736f-py2.py3-none-any.whl

Smoke test screenshot

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