chore: retire asdf

[krukonshedul]

What changed in this repo

• Removed the obsolete ImageOS: ubuntu22 line from the env: block in .github/workflows/ci.yaml (only workflow file with this pin). The neighboring RUNNER_OS comment was left intact since it documents RUNNER_OS/setup-beam version matching, not solely ImageOS.
• Bumped action pins via the internal alflow lockfile chain (produce -> bump-internal -> produce -> pin-external --pin-all -> produce).

Part of the org-wide asdf retirement rollout.

[kpiotr]

Approved — mechanical asdf retirement, verified:

• Every deleted .tool-versions is covered by a mise.toml/.mise.toml at head with identical tool versions (same directory, or an ancestor config declaring the same pins).
• No .tool-versions file left behind at head.
• No workflow, script, Dockerfile, or Taskfile at head still reads the deleted file as a live input — remaining mentions are comments, dead paths: filter entries, continue-on-error steps, or inputs the bumped platform-tribe-actions pin no longer declares.
• Action pins move consistently to platform-tribe-actions@7f48a2b1a03f0df7c865685b657068a80db68bad, and the removed steps.versions.outputs.* consumers go away with the step that produced them.
• CI green on head with no pending or failing required checks.

[krukonshedul]

Superseded by #77 and #79, both merged: #77 removed .github/actions.lock.yaml from VCS, and #79 removed the ImageOS/RUNNER_OS env vars from ci.yaml (this branch's only substantive change) and regenerated mise.lock/actions.lock.yaml in the newer format. Closing as no longer needed.