Potential fix for code scanning alert no. 48: Clear-text logging of sensitive information

[whyseu]

Potential fix for https://github.com/agent-network-protocol/anp/security/code-scanning/48

In general, the fix is to stop logging the sensitive secret_key_id value in clear text. For this specific example, we can keep the informational log while redacting the actual identifier, so behaviour is unchanged except for what appears in stdout.

The best minimal change is to modify the print in example_dispatch_incoming_message in examples/python/e2e_encryption_v2_examples/key_manager_example.py so it no longer interpolates secret_key_id. Instead, we can either state that a secret key ID was generated, or include only a non-sensitive derived representation (e.g., a fixed placeholder or a short, non-identifying hash). To avoid introducing new dependencies or functionality, we’ll simply remove the interpolation and mention the existence of the ID generically. No other files need changes, because the alerts in message_builder.py and session.py are about data flow into this sink, not about those functions logging directly.

Concretely:

• In examples/python/e2e_encryption_v2_examples/key_manager_example.py, on line 194, replace
  print(f"[步骤 2] Alice 发送加密消息, secret_key_id={secret_key_id}")
  with a message that does not reveal secret_key_id, such as
  print("[步骤 2] Alice 发送加密消息（已生成 secret_key_id）").
• No new imports or helper methods are required.

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