The stub previously panicked on all methods including NewKeychainUnlocker,
which is called from vault code when processing keychain-type unlocker
metadata. This caused crashes on Linux/Windows when a vault synced from
macOS contained keychain unlockers.
Now returns proper error values, allowing graceful degradation and
cross-platform vault portability.
- Add build tags to keychain implementation files (Darwin-only)
- Create stub implementations for non-Darwin platforms that panic
- Conditionally show keychain support in help text based on platform
- Platform check in UnlockersAdd prevents keychain usage on non-Darwin
- Verified GPG operations already protected against command injection
via validateGPGKeyID() and proper exec.Command argument passing
- Keychain operations use go-keychain library, no shell commands
The application now builds and runs on Linux/non-Darwin platforms with
keychain functionality properly isolated to macOS only.