fix(runtime): export policy engine module

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

rust/crates/runtime/src/lib.rs

@@ -14,7 +14,7 @@ mod mcp_stdio;
 pub mod mcp_tool_bridge;
 mod oauth;
 pub mod permission_enforcer;
-mod policy_engine;
+pub mod policy_engine;
 mod permissions;
 mod prompt;
 mod remote;