[Feature]: recall_history_python is silently not registered when no sandbox is available (kernel < 5.13, no Landlock)

Symptom

On kernel 5.10 (< 5.13, no Landlock) the log shows:

scroll: sandbox unavailable or disabled for recall_history_python
        — registering only the structured recall_history tool

Only the structured recall_history (expand / search / recall_tool) reaches the model; the advanced recall REPL is gone entirely, with no explicit degradation notice to either the model or the user.

Notes

I understand this is deliberate (runtime/builder.py: with no sandbox every call fails closed, the guard layer misreads DENIED as a sandbox violation and turns it into recurring approval prompts). This is not a request to re-enable an unsafe path. Two asks:

1. Make the degradation visible — the model/user should know that advanced recall is unavailable and why, instead of silently losing it.
2. Advanced recall should not hard-depend on Landlock — e.g. expose the read-only query surface of recall_history_python as part of the structured tool, or provide an explicitly opt-in fallback.

Environment: kernel 5.10, container, QwenPaw 2.2.x.