fix(core): clarify request permissions results

Return model-visible status and guidance from `request_permissions` so
follow-up turns know the UI decision has already resolved. This keeps
approved permissions framed as active instead of pending approval.

Update prompt and tool descriptions with the same contract, and cover the
granted and denied output shapes plus the follow-up request payload.

codex-rs/protocol/src/models.rs

@@ -636,7 +636,7 @@ fn granular_prompt_intro_text() -> &'static str {
 }
 
 fn request_permissions_tool_prompt_section() -> &'static str {
-    "# request_permissions Tool\n\nThe built-in `request_permissions` tool is available in this session. Invoke it immediately when the user asks conversationally to allow specific filesystem or network access, for example \"allow writing to ~/Downloads in this session\" or \"grant access to /tmp/output\". Request only the specific permissions required. Set `scope` to `session` when the user explicitly asks for session-long access; otherwise use `turn`."
+    "# request_permissions Tool\n\nThe built-in `request_permissions` tool is available in this session. Invoke it immediately when the user asks conversationally to allow specific filesystem or network access, for example \"allow writing to ~/Downloads in this session\" or \"grant access to /tmp/output\". Request only the specific permissions required. Set `scope` to `session` when the user explicitly asks for session-long access; otherwise use `turn`. After this tool returns, the user has already approved or denied the request in the UI. If permissions were granted, treat them as active now; do not say \"once you approve\" or ask the user to approve the same request again. If no permissions were granted, say the request was not approved."
 }
 
 fn request_permission_preset_tool_prompt_section() -> &'static str {
@@ -1811,6 +1811,8 @@ mod tests {
         let text = instructions.into_text();
         assert!(text.contains("`approval_policy` is `unless-trusted`"));
         assert!(text.contains("# request_permissions Tool"));
+        assert!(text.contains("After this tool returns, the user has already approved or denied"));
+        assert!(text.contains("do not say \"once you approve\""));
     }
 
     #[test]