Update render name in tui for approval_policy to match with config values (#1675)

Currently, codex on start shows the value for the approval policy as
name of
[AskForApproval](2437a8d17a/codex-rs/core/src/protocol.rs (L128))
enum, which differs from
[approval_policy](2437a8d17a/codex-rs/config.md (approval_policy))
config values.
E.g. "untrusted" becomes "UnlessTrusted", "on-failure" -> "OnFailure",
"never" -> "Never".
This PR changes render names of the approval policy to match with
configuration values.

codex-rs/tui/src/history_cell.rs

@@ -156,7 +156,7 @@ impl HistoryCell {
                 ("workdir", config.cwd.display().to_string()),
                 ("model", config.model.clone()),
                 ("provider", config.model_provider_id.clone()),
-                ("approval", format!("{:?}", config.approval_policy)),
+                ("approval", config.approval_policy.to_string()),
                 ("sandbox", summarize_sandbox_policy(&config.sandbox_policy)),
             ];
             if config.model_provider.wire_api == WireApi::Responses