feat(core): persist network approvals in execpolicy (#12357)

## Summary
Persist network approval allow/deny decisions as `network_rule(...)`
entries in execpolicy (not proxy config)

It adds `network_rule` parsing + append support in `codex-execpolicy`,
including `decision="prompt"` (parse-only; not compiled into proxy
allow/deny lists)
- compile execpolicy network rules into proxy allow/deny lists and
update the live proxy state on approval
- preserve requirements execpolicy `network_rule(...)` entries when
merging with file-based execpolicy
- reject broad wildcard hosts (for example `*`) for persisted
`network_rule(...)`

codex-rs/app-server-protocol/schema/json/EventMsg.json

@@ -1662,6 +1662,16 @@
                 "null"
               ]
             },
+            "proposed_network_policy_amendments": {
+              "description": "Proposed network policy amendments (for example allow/deny this host in future).",
+              "items": {
+                "$ref": "#/definitions/NetworkPolicyAmendment"
+              },
+              "type": [
+                "array",
+                "null"
+              ]
+            },
             "reason": {
               "description": "Optional human-readable reason for the approval (e.g. retry without sandbox).",
               "type": [
@@ -3637,6 +3647,28 @@
       ],
       "type": "string"
     },
+    "NetworkPolicyAmendment": {
+      "properties": {
+        "action": {
+          "$ref": "#/definitions/NetworkPolicyRuleAction"
+        },
+        "host": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "action",
+        "host"
+      ],
+      "type": "object"
+    },
+    "NetworkPolicyRuleAction": {
+      "enum": [
+        "allow",
+        "deny"
+      ],
+      "type": "string"
+    },
     "ParsedCommand": {
       "oneOf": [
         {
@@ -6907,6 +6939,16 @@
             "null"
           ]
         },
+        "proposed_network_policy_amendments": {
+          "description": "Proposed network policy amendments (for example allow/deny this host in future).",
+          "items": {
+            "$ref": "#/definitions/NetworkPolicyAmendment"
+          },
+          "type": [
+            "array",
+            "null"
+          ]
+        },
         "reason": {
           "description": "Optional human-readable reason for the approval (e.g. retry without sandbox).",
           "type": [