fix(apple): restore WhenUnlockedThisDeviceOnly for SE key access control#160
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PR #158 blanket-replaced all protection classes to AfterFirstUnlockThisDeviceOnly, including makeAccessControl() which sets the Secure Enclave key's access control at generation time. This broke CryptoKit's touchIDAuthenticationAllowableReuseDuration — every sign required Touch ID instead of caching biometric auth. Since the SE key's access control is immutable after creation, fixing this requires regenerating all affected keys. The keychain wrapping key (keychain_store) correctly uses AfterFirstUnlockThisDeviceOnly for sleep/wake survival. The SE key access control must use WhenUnlockedThisDeviceOnly for biometric caching. These are separate decisions with different requirements. Also adds AGENTS.md with protection class safety rules and updates CLAUDE.md to document the split, so this class of mistake is prevented in future changes.
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Summary
AfterFirstUnlockThisDeviceOnly, includingmakeAccessControl()which controls the SE key's access control at generation time. This broke CryptoKit'stouchIDAuthenticationAllowableReuseDuration— every sign required Touch ID instead of caching biometric auth within the TTL window.makeAccessControl()back tokSecAttrAccessibleWhenUnlockedThisDeviceOnlywhile keepingkeychain_store()atkSecAttrAccessibleAfterFirstUnlockThisDeviceOnly(correct for sleep/wake survival).AGENTS.mdwith protection class safety rules and updatesCLAUDE.mdto document the split, preventing this class of mistake from recurring.Impact: Keys generated after the PR #158 change have the wrong SE access control baked into the SEP. Since the SE key access control is immutable after creation, affected keys must be regenerated.
Test plan
cargo test --workspacepassescargo clippy --workspace --all-targets -- -D warningscleanAfterFirstUnlockThisDeviceOnly)