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/linux-sandbox/tests/suite/landlock.rs

@@ -76,6 +76,7 @@ async fn run_cmd_result_with_writable_roots(
         expiration: timeout_ms.into(),
         env: create_env_from_core_vars(),
         network: None,
+        network_attempt_id: None,
         sandbox_permissions: SandboxPermissions::UseDefault,
         windows_sandbox_level: WindowsSandboxLevel::Disabled,
         justification: None,
@@ -123,7 +124,7 @@ async fn should_skip_bwrap_tests() -> bool {
     .await
     {
         Ok(output) => is_bwrap_unavailable_output(&output),
-        Err(CodexErr::Sandbox(SandboxErr::Denied { output })) => {
+        Err(CodexErr::Sandbox(SandboxErr::Denied { output, .. })) => {
             is_bwrap_unavailable_output(&output)
         }
         // Probe timeouts are not actionable for the bwrap-specific assertions below;
@@ -142,7 +143,7 @@ fn expect_denied(
             assert_ne!(output.exit_code, 0, "{context}: expected nonzero exit code");
             output
         }
-        Err(CodexErr::Sandbox(SandboxErr::Denied { output })) => *output,
+        Err(CodexErr::Sandbox(SandboxErr::Denied { output, .. })) => *output,
         Err(err) => panic!("{context}: {err:?}"),
     }
 }
@@ -236,6 +237,7 @@ async fn assert_network_blocked(cmd: &[&str]) {
         expiration: NETWORK_TIMEOUT_MS.into(),
         env: create_env_from_core_vars(),
         network: None,
+        network_attempt_id: None,
         sandbox_permissions: SandboxPermissions::UseDefault,
         windows_sandbox_level: WindowsSandboxLevel::Disabled,
         justification: None,
@@ -257,7 +259,7 @@ async fn assert_network_blocked(cmd: &[&str]) {
 
     let output = match result {
         Ok(output) => output,
-        Err(CodexErr::Sandbox(SandboxErr::Denied { output })) => *output,
+        Err(CodexErr::Sandbox(SandboxErr::Denied { output, .. })) => *output,
         _ => {
             panic!("expected sandbox denied error, got: {result:?}");
         }