Summary

Support an immutable operator defaults/policy file (for example SYSTEM_TOOLS.md semantics) that agents cannot edit at runtime.

Why

Some enterprise deployments need a non-editable baseline for tool policy and system constraints. The current setup relies on editable config and prompt files, which is hard to lock down as a policy primitive.

Requested behavior

1. Define a non-editable defaults/policy source loaded on startup.
2. Merge policy in a deterministic precedence order (policy > user overrides where applicable).
3. Expose read-only visibility of effective policy in status/doctor output.
4. Prevent agent/runtime writes that would weaken locked policy.

Related

• Potentially adjacent to filesystem and tool policy controls, but this asks for an explicit immutable policy layer.