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/config/config_tests.rs

@@ -9554,6 +9554,7 @@ async fn trace_exporter_defaults_to_none_when_log_exporter_is_set() -> std::io::
     let fixture = create_test_fixture()?;
     let mut cfg = fixture.cfg.clone();
     cfg.otel = Some(OtelConfigToml {
+        tool_result: toml::from_str("max_bytes = 8192").expect("tool-result logging config"),
         exporter: Some(OtelExporterKind::OtlpHttp {
             endpoint: "http://localhost:14318/v1/logs".to_string(),
             headers: HashMap::new(),
@@ -9574,6 +9575,7 @@ async fn trace_exporter_defaults_to_none_when_log_exporter_is_set() -> std::io::
     )
     .await?;
 
+    assert_eq!(config.otel.tool_result.max_bytes, 8192);
     assert!(matches!(
         config.otel.exporter,
         OtelExporterKind::OtlpHttp { .. }

codex-rs/core/src/config/otel.rs

@@ -26,6 +26,7 @@ pub(crate) fn resolve_config(
     let tracestate = resolve_tracestate(config.tracestate, startup_warnings);
 
     OtelConfig {
+        tool_result: config.tool_result,
         log_user_prompt,
         environment,
         exporter,