refactor: cleanup debug prints and remove unsafe panics

[mk0walsk]

This PR performs a general cleanup of debug artifacts and unsafe error handling practices.

Changes:

1. pkg/secretstore: Removed an accidental fmt.Println debug statement in secret_store_messages.go that was polluting stdout.
2. pkg/rendezvous: Removed an unreachable panic in rendezvous.go. hmac.Write is documented to never return an error in the standard library, making this check unnecessary and the panic unsafe for a library.
3. pkg/*-driver: Changed fallback logging from stdout to stderr in CGO bridges (cgo_bridge.go, bridge_darwin.go) to prevent interfering with standard output streams when the logger is not initialized.