chore: add a separate reject-policy flag for skill approvals (#14271)

## Summary
- add `skill_approval` to `RejectConfig` and the app-server v2
`AskForApproval::Reject` payload so skill-script prompts can be
configured independently from sandbox and rule-based prompts
- update Unix shell escalation to reject prompts based on the actual
decision source, keeping prefix rules tied to `rules`, unmatched command
fallbacks tied to `sandbox_approval`, and skill scripts tied to
`skill_approval`
- regenerate the affected protocol/config schemas and expand
unit/integration coverage for the new flag and skill approval behavior

codex-rs/protocol/src/protocol.rs

@@ -533,6 +533,9 @@ pub struct RejectConfig {
     pub sandbox_approval: bool,
     /// Reject prompts triggered by execpolicy `prompt` rules.
     pub rules: bool,
+    /// Reject approval prompts triggered by skill script execution.
+    #[serde(default)]
+    pub skill_approval: bool,
     /// Reject approval prompts related to built-in permission requests.
     #[serde(default)]
     pub request_permissions: bool,
@@ -549,6 +552,10 @@ impl RejectConfig {
         self.rules
     }
 
+    pub const fn rejects_skill_approval(self) -> bool {
+        self.skill_approval
+    }
+
     pub const fn rejects_request_permissions(self) -> bool {
         self.request_permissions
     }
@@ -3457,6 +3464,7 @@ mod tests {
             RejectConfig {
                 sandbox_approval: false,
                 rules: false,
+                skill_approval: false,
                 request_permissions: false,
                 mcp_elicitations: true,
             }
@@ -3466,6 +3474,7 @@ mod tests {
             !RejectConfig {
                 sandbox_approval: false,
                 rules: false,
+                skill_approval: false,
                 request_permissions: false,
                 mcp_elicitations: false,
             }
@@ -3473,12 +3482,37 @@ mod tests {
         );
     }
 
+    #[test]
+    fn reject_config_skill_approval_flag_is_field_driven() {
+        assert!(
+            RejectConfig {
+                sandbox_approval: false,
+                rules: false,
+                skill_approval: true,
+                request_permissions: false,
+                mcp_elicitations: false,
+            }
+            .rejects_skill_approval()
+        );
+        assert!(
+            !RejectConfig {
+                sandbox_approval: false,
+                rules: false,
+                skill_approval: false,
+                request_permissions: false,
+                mcp_elicitations: false,
+            }
+            .rejects_skill_approval()
+        );
+    }
+
     #[test]
     fn reject_config_request_permissions_flag_is_field_driven() {
         assert!(
             RejectConfig {
                 sandbox_approval: false,
                 rules: false,
+                skill_approval: false,
                 request_permissions: true,
                 mcp_elicitations: false,
             }
@@ -3488,6 +3522,7 @@ mod tests {
             !RejectConfig {
                 sandbox_approval: false,
                 rules: false,
+                skill_approval: false,
                 request_permissions: false,
                 mcp_elicitations: false,
             }
@@ -3496,7 +3531,7 @@ mod tests {
     }
 
     #[test]
-    fn reject_config_defaults_missing_request_permissions_to_false() {
+    fn reject_config_defaults_missing_optional_flags_to_false() {
         let decoded = serde_json::from_value::<RejectConfig>(serde_json::json!({
             "sandbox_approval": true,
             "rules": false,
@@ -3509,6 +3544,7 @@ mod tests {
             RejectConfig {
                 sandbox_approval: true,
                 rules: false,
+                skill_approval: false,
                 request_permissions: false,
                 mcp_elicitations: true,
             }