flaker storage cache on GitHub Actions

flaker keeps its data in a DuckDB file at the path declared by flaker.toml [storage] path (default .flaker/data). For flaky detection / KPI / quarantine to work, that file must persist between CI runs. GitHub Actions has no first-class runtime storage, so the convention is actions/cache@v4 with a sliding key.

When this skill applies

• "新しい repo に flaker を CI で動かす"
• "flaker の履歴が CI で消えてる / 毎回ゼロからになる"
• "flaker に を import するワークフロー追加して"
• "VRT / playwright / custom-adapter report を flaker に流したい"

Cache key shape