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/app-server-protocol/schema/json/v1/ResumeConversationResponse.json

@@ -1438,6 +1438,17 @@
               "description": "The command's working directory.",
               "type": "string"
             },
+            "network_approval_context": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/NetworkApprovalContext"
+                },
+                {
+                  "type": "null"
+                }
+              ],
+              "description": "Optional network context for a blocked request that can be approved."
+            },
             "parsed_cmd": {
               "items": {
                 "$ref": "#/definitions/ParsedCommand"
@@ -3315,6 +3326,30 @@
       ],
       "type": "string"
     },
+    "NetworkApprovalContext": {
+      "properties": {
+        "host": {
+          "type": "string"
+        },
+        "protocol": {
+          "$ref": "#/definitions/NetworkApprovalProtocol"
+        }
+      },
+      "required": [
+        "host",
+        "protocol"
+      ],
+      "type": "object"
+    },
+    "NetworkApprovalProtocol": {
+      "enum": [
+        "http",
+        "https",
+        "socks5_tcp",
+        "socks5_udp"
+      ],
+      "type": "string"
+    },
     "ParsedCommand": {
       "oneOf": [
         {