fix: clean up elicitation used by exec-server (openai#6958)

Using appropriate message/title fields, I think this looks better now:

<img width="3370" height="3208" alt="image"
src="https://github.com/user-attachments/assets/e9bbf906-4ba8-4563-affc-62cdc6c97342"
/>

Though note that in the current version of the Inspector (`0.17.2`), you
cannot hit **Submit** until you fill out the field. I believe this is a
bug in the Inspector, as it does not properly handle the case when all
fields are optional. I put up a fix:

modelcontextprotocol/inspector#926

Author: bolinfest

codex-rs/exec-server/src/posix/mcp_escalation_policy.rs

@@ -6,8 +6,6 @@ use rmcp::model::CreateElicitationRequestParam;
 use rmcp::model::CreateElicitationResult;
 use rmcp::model::ElicitationAction;
 use rmcp::model::ElicitationSchema;
-use rmcp::model::PrimitiveSchema;
-use rmcp::model::StringSchema;
 use rmcp::service::RequestContext;
 
 use crate::posix::escalate_protocol::EscalateAction;
@@ -54,12 +52,19 @@ impl McpEscalationPolicy {
         context
             .peer
             .create_elicitation(CreateElicitationRequestParam {
-                message: format!("Allow Codex to run `{command:?}` in `{workdir:?}`?"),
-                #[allow(clippy::expect_used)]
+                message: format!("Allow agent to run `{command}` in `{}`?", workdir.display()),
                 requested_schema: ElicitationSchema::builder()
-                    .property("dummy", PrimitiveSchema::String(StringSchema::new()))
+                    .title("Execution Permission Request")
+                    .optional_string_with("reason", |schema| {
+                        schema.description("Optional reason for allowing or denying execution")
+                    })
                     .build()
-                    .expect("failed to build elicitation schema"),
+                    .map_err(|e| {
+                        McpError::internal_error(
+                            format!("failed to build elicitation schema: {e}"),
+                            None,
+                        )
+                    })?,
             })
             .await
             .map_err(|e| McpError::internal_error(e.to_string(), None))