guardian initial feedback / tweaks (#13897)

## Summary
- remove the remaining model-visible guardian-specific `on-request`
prompt additions so enabling the feature does not change the main
approval-policy instructions
- neutralize user-facing guardian wording to talk about automatic
approval review / approval requests rather than a second reviewer or
only sandbox escalations
- tighten guardian retry-context handling so agent-authored
`justification` stays in the structured action JSON and is not also
injected as raw retry context
- simplify guardian review plumbing in core by deleting dead
prompt-append paths and trimming some request/transcript setup code

## Notable Changes
- delete the dead `permissions/approval_policy/guardian.md` append path
and stop threading `guardian_approval_enabled` through model-facing
developer-instruction builders
- rename the experimental feature copy to `Automatic approval review`
and update the `/experimental` snapshot text accordingly
- make approval-review status strings generic across shell, patch,
network, and MCP review types
- forward real sandbox/network retry reasons for shell and unified-exec
guardian review, but do not pass agent-authored justification as raw
retry context
- simplify `guardian.rs` by removing the one-field request wrapper,
deduping reasoning-effort selection, and cleaning up transcript entry
collection

## Testing
- `just fmt`
- full validation left to CI

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/protocol/src/models.rs

@@ -408,8 +408,6 @@ const APPROVAL_POLICY_ON_REQUEST_RULE: &str =
     include_str!("prompts/permissions/approval_policy/on_request_rule.md");
 const APPROVAL_POLICY_ON_REQUEST_RULE_REQUEST_PERMISSION: &str =
     include_str!("prompts/permissions/approval_policy/on_request_rule_request_permission.md");
-const GUARDIAN_APPROVAL_FEATURE: &str =
-    include_str!("prompts/permissions/approval_policy/guardian.md");
 
 const SANDBOX_MODE_DANGER_FULL_ACCESS: &str =
     include_str!("prompts/permissions/sandbox_mode/danger_full_access.md");
@@ -427,7 +425,6 @@ impl DeveloperInstructions {
 
     pub fn from(
         approval_policy: AskForApproval,
-        guardian_approval_enabled: bool,
         exec_policy: &Policy,
         request_permission_enabled: bool,
     ) -> DeveloperInstructions {
@@ -451,14 +448,7 @@ impl DeveloperInstructions {
             AskForApproval::Never => APPROVAL_POLICY_NEVER.to_string(),
             AskForApproval::UnlessTrusted => APPROVAL_POLICY_UNLESS_TRUSTED.to_string(),
             AskForApproval::OnFailure => APPROVAL_POLICY_ON_FAILURE.to_string(),
-            AskForApproval::OnRequest => {
-                let mut instructions = on_request_instructions();
-                if guardian_approval_enabled {
-                    instructions.push_str("\n\n");
-                    instructions.push_str(GUARDIAN_APPROVAL_FEATURE);
-                }
-                instructions
-            }
+            AskForApproval::OnRequest => on_request_instructions(),
             AskForApproval::Reject(reject_config) => {
                 let on_request_instructions = on_request_instructions();
                 let sandbox_approval = reject_config.sandbox_approval;
@@ -521,7 +511,6 @@ impl DeveloperInstructions {
     pub fn from_policy(
         sandbox_policy: &SandboxPolicy,
         approval_policy: AskForApproval,
-        guardian_approval_enabled: bool,
         exec_policy: &Policy,
         cwd: &Path,
         request_permission_enabled: bool,
@@ -546,7 +535,6 @@ impl DeveloperInstructions {
             sandbox_mode,
             network_access,
             approval_policy,
-            guardian_approval_enabled,
             exec_policy,
             writable_roots,
             request_permission_enabled,
@@ -571,7 +559,6 @@ impl DeveloperInstructions {
         sandbox_mode: SandboxMode,
         network_access: NetworkAccess,
         approval_policy: AskForApproval,
-        guardian_approval_enabled: bool,
         exec_policy: &Policy,
         writable_roots: Option<Vec<WritableRoot>>,
         request_permission_enabled: bool,
@@ -585,7 +572,6 @@ impl DeveloperInstructions {
             ))
             .concat(DeveloperInstructions::from(
                 approval_policy,
-                guardian_approval_enabled,
                 exec_policy,
                 request_permission_enabled,
             ))
@@ -1667,7 +1653,6 @@ mod tests {
             SandboxMode::WorkspaceWrite,
             NetworkAccess::Enabled,
             AskForApproval::OnRequest,
-            false,
             &Policy::empty(),
             None,
             false,
@@ -1697,7 +1682,6 @@ mod tests {
         let instructions = DeveloperInstructions::from_policy(
             &policy,
             AskForApproval::UnlessTrusted,
-            false,
             &Policy::empty(),
             &PathBuf::from("/tmp"),
             false,
@@ -1720,7 +1704,6 @@ mod tests {
             SandboxMode::WorkspaceWrite,
             NetworkAccess::Enabled,
             AskForApproval::OnRequest,
-            false,
             &exec_policy,
             None,
             false,
@@ -1738,7 +1721,6 @@ mod tests {
             SandboxMode::WorkspaceWrite,
             NetworkAccess::Enabled,
             AskForApproval::OnRequest,
-            false,
             &Policy::empty(),
             None,
             true,
@@ -1749,23 +1731,6 @@ mod tests {
         assert!(text.contains("additional_permissions"));
     }
 
-    #[test]
-    fn includes_guardian_feature_guidance_for_on_request_when_enabled() {
-        let instructions = DeveloperInstructions::from_permissions_with_network(
-            SandboxMode::WorkspaceWrite,
-            NetworkAccess::Enabled,
-            AskForApproval::OnRequest,
-            true,
-            &Policy::empty(),
-            None,
-            false,
-        );
-
-        let text = instructions.into_text();
-        assert!(text.contains("guardian subagent"));
-        assert!(text.contains("approval prompts"));
-    }
-
     #[test]
     fn render_command_prefix_list_sorts_by_len_then_total_len_then_alphabetical() {
         let prefixes = vec![