Return trusted directories paired with their approval timestamps.
The audit surface for the trusted_at metadata that trust_skill_dir
records: list_trusted_skill_dirs returns only paths (all enforcement
needs), so this is the one reader of the timestamp, used by skills trust list to show when each directory was approved.
Path to the trust store file. Defaults to
~/.deepagents/.state/skill_trust.json.
Propagated to _load_store; see list_trusted_skill_dirs.
