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/core/src/tools/runtimes/shell/unix_escalation.rs

@@ -7,7 +7,7 @@ use crate::exec::SandboxType;
 use crate::exec::is_likely_sandbox_denied;
 use crate::exec_policy::prompt_is_rejected_by_policy;
 use crate::features::Feature;
-use crate::guardian::GuardianReviewRequest;
+use crate::guardian::GuardianApprovalRequest;
 use crate::guardian::review_approval_request;
 use crate::guardian::routes_approval_to_guardian;
 use crate::sandboxing::ExecRequest;
@@ -50,7 +50,6 @@ use codex_shell_escalation::PreparedExec;
 use codex_shell_escalation::ShellCommandExecutor;
 use codex_shell_escalation::Stopwatch;
 use codex_utils_absolute_path::AbsolutePathBuf;
-use serde_json::json;
 use std::collections::HashMap;
 use std::path::PathBuf;
 use std::sync::Arc;
@@ -386,16 +385,19 @@ impl CoreShellActionProvider {
         Ok(stopwatch
             .pause_for(async move {
                 if routes_approval_to_guardian(&turn) {
-                    let request = GuardianReviewRequest {
-                        action: json!({
-                            "tool": tool_name,
-                            "program": program,
-                            "argv": argv,
-                            "cwd": workdir,
-                            "additional_permissions": additional_permissions,
-                        }),
-                    };
-                    return review_approval_request(&session, &turn, request, None).await;
+                    return review_approval_request(
+                        &session,
+                        &turn,
+                        GuardianApprovalRequest::Execve {
+                            tool_name: tool_name.to_string(),
+                            program: program.to_string_lossy().into_owned(),
+                            argv: argv.to_vec(),
+                            cwd: workdir,
+                            additional_permissions,
+                        },
+                        None,
+                    )
+                    .await;
                 }
                 let available_decisions = vec![
                     Some(ReviewDecision::Approved),