test(06-05): integration tests for keys list/show/export/delete
- Temp-file SQLite DB seeded with three findings (2 openai, 1 anthropic,
one verified) via storage.SaveFinding + loadOrCreateEncKey
- RunE + cmd.SetOut buffers for hermetic stdout capture
- Covers: list default + provider filter, show hit (unmasked) + miss,
export JSON stdout (parses + plaintext present), export CSV to file
(header + 3 rows), delete --yes then list returns 2
- TestKeysCopy and TestKeysVerify are documented as intentionally skipped
(clipboard backend unavailable headlessly; verify needs network)
e2394ec663