- Replace AgeKeySource+retrieve() with IdentitySource+load() returning Box<dyn Identity> - Rewrite bitwarden/file/prompt sources to implement new trait - Add resolve_identities() public API with partial-success semantics - Delete _legacy.rs and remove legacy re-exports from lib.rs - Update integration tests to use new API Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>