Make tool-result telemetry limits configurable (#39779)

## What changed

- Add `otel.tool_result.max_bytes`, defaulting to 2048 bytes, to control the
  text included in `codex.tool_result` logs independently of model-visible
  output limits.
- Apply truncation centrally when emitting telemetry, preserve UTF-8
  boundaries, and report whether the logged output was truncated.
- Record typed tool names and namespaces, agent names, and process-local result
  sequence numbers while keeping tool arguments and output out of trace events.

## Testing

- Cover configuration propagation, UTF-8-safe truncation, raw tool-output
  logging, and log/trace event routing and fields.

GitOrigin-RevId: 89ca76e55f1a09b729e7770ce01f2e4d98f9a22d

codex-rs/core/src/session/session.rs

@@ -1067,7 +1067,8 @@ impl Session {
                 terminal_type.clone(),
                 session_configuration.session_source.clone(),
             )
-            .with_auth_env(auth_env_telemetry.to_otel_metadata());
+            .with_auth_env(auth_env_telemetry.to_otel_metadata())
+            .with_tool_result_log_config(config.otel.tool_result);
             if let Some(service_name) = session_configuration.metrics_service_name.as_deref() {
                 session_telemetry = session_telemetry.with_metrics_service_name(service_name);
             }