fix: improve key derivation and logging

- Fix mnemonic validation in Python version
- Add consistent output logging across Python/TypeScript
- Show key derivation details in readable format
- Truncate sensitive values in output
- Match output format between implementations

This fixes the mnemonic error and improves debugging by
adding consistent logging of the key derivation process.

test-scripts/new_flow.py

@@ -94,6 +94,10 @@ def derive_address(
     public_key = pk.public_key
     public_hex = public_key.to_hex()[2:]  # Remove '0x' prefix
 
+    print(f"  Address: {address}")
+    print(f"  Private Key: {private_hex[:8]}...")
+    print(f"  Public Key: {public_hex[:8]}...")
+
     return address, private_hex, public_hex, derivation_path
 
 def new_identifier(