feat(core): add structured network approval plumbing and policy decision model (#11672)

### Description
#### Summary
Introduces the core plumbing required for structured network approvals

#### What changed
- Added structured network policy decision modeling in core.
- Added approval payload/context types needed for network approval
semantics.
- Wired shell/unified-exec runtime plumbing to consume structured
decisions.
- Updated related core error/event surfaces for structured handling.
- Updated protocol plumbing used by core approval flow.
- Included small CLI debug sandbox compatibility updates needed by this
layer.

#### Why
establishes the minimal backend foundation for network approvals without
yet changing high-level orchestration or TUI behavior.

#### Notes
- Behavior remains constrained by existing requirements/config gating.
- Follow-up PRs in the stack handle orchestration, UX, and app-server
integration.

---------

Co-authored-by: Codex <199175422+chatgpt-codex-connector[bot]@users.noreply.github.com>

codex-rs/cli/src/debug_sandbox.rs

@@ -213,12 +213,19 @@ async fn run_command_under_sandbox(
     #[cfg(not(target_os = "macos"))]
     let _ = log_denials;
 
+    let managed_network_requirements_enabled = config.managed_network_requirements_enabled();
+
     // This proxy should only live for the lifetime of the child process.
     let network_proxy = match config.permissions.network.as_ref() {
         Some(spec) => Some(
-            spec.start_proxy()
-                .await
-                .map_err(|err| anyhow::anyhow!("failed to start managed network proxy: {err}"))?,
+            spec.start_proxy(
+                config.permissions.sandbox_policy.get(),
+                None,
+                None,
+                managed_network_requirements_enabled,
+            )
+            .await
+            .map_err(|err| anyhow::anyhow!("failed to start managed network proxy: {err}"))?,
         ),
         None => None,
     };