fix(ci): make the clean-machine failures diagnosable, then green (#9)

[phmatray]

Implements #9.

Closes #9.

Executing the implementation plan task-by-task; the checklist below — and the plan on the issue — are ticked as each task lands. Opened as a draft — will be marked ready after the final task and a code-review pass.

Plan

• Task 1: CI says WHY a user unit failed
• Task 2: a fresh install names wallpapers it actually installs
• Task 3: dispose of the three failing units on Task 1's evidence

🤖 Generated with Claude Code

https://claude.ai/code/session_01SYBhT1xfp3MQ1w3687F4Mp

[phmatray]

Recorded, not filed: .claude/decision-events.jsonl is not git-ignored

Hit while merging this PR — decide.sh refused to write its telemetry:

decide: refusing to write .claude/decision-events.jsonl — git does not ignore it, and an agent's
        telemetry must never become a commit in someone else's repository.

The verdict was unaffected (the script says so, and it is right to refuse). But the kit's decision log is silently off in all ten macarchy repos, so the event counts it exists to produce are not being collected anywhere.

Not filed as an issue on purpose: the fix is one .gitignore line per repo, in ten repos — the same shape as the two worktree-home lines added in 962e4f7 and its siblings, which were done directly rather than tracked. It earns a record, not a queue item; a repo that never runs an agent does not need it at all.

This is the third artifact of the same class (.claude/worktrees/, .worktrees/, and now this one), which suggests the durable fix is one ignore stanza covering .claude/ agent scratch rather than a line per artifact as each is discovered.