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/protocol/src/approvals.rs

@@ -37,6 +37,24 @@ impl From<Vec<String>> for ExecPolicyAmendment {
     }
 }
 
+#[derive(Debug, Clone, Copy, Deserialize, Serialize, PartialEq, Eq, JsonSchema, TS)]
+#[serde(rename_all = "snake_case")]
+pub enum NetworkApprovalProtocol {
+    // TODO(viyatb): Add websocket protocol variants when managed proxy policy
+    // decisions expose websocket traffic as a distinct approval context.
+    Http,
+    #[serde(alias = "https_connect", alias = "http-connect")]
+    Https,
+    Socks5Tcp,
+    Socks5Udp,
+}
+
+#[derive(Debug, Clone, Deserialize, Serialize, PartialEq, Eq, JsonSchema, TS)]
+pub struct NetworkApprovalContext {
+    pub host: String,
+    pub protocol: NetworkApprovalProtocol,
+}
+
 #[derive(Debug, Clone, Deserialize, Serialize, JsonSchema, TS)]
 pub struct ExecApprovalRequestEvent {
     /// Identifier for the associated exec call, if available.
@@ -52,6 +70,10 @@ pub struct ExecApprovalRequestEvent {
     /// Optional human-readable reason for the approval (e.g. retry without sandbox).
     #[serde(skip_serializing_if = "Option::is_none")]
     pub reason: Option<String>,
+    /// Optional network context for a blocked request that can be approved.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[ts(optional)]
+    pub network_approval_context: Option<NetworkApprovalContext>,
     /// Proposed execpolicy amendment that can be applied to allow future runs.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     #[ts(optional)]