smoke.sh cleans up its state root

[0xLeif]

From PR #1 review nits.

smoke.sh writes to the real ~/.aps and the runner's UserDefaults, then resets values but leaves the directory behind. Once --state-dir exists, point smoke at a mktemp dir with a trap cleanup.

Acceptance criteria

• smoke.sh leaves no trace in $HOME (dir or defaults)
• Still exercises the default path in at least one assertion

[0xLeif]

Shipped in PR #2 (aps 0.2.0, merge commit 62198af). Verified in review: gates green, behavior confirmed locally.