[codex] Initialize exec-server OpenTelemetry at startup (#25019)

## Summary

- Initialize stderr tracing and the configured OpenTelemetry provider
for local and remote `codex exec-server` startup.
- Instrument the local and remote server entrypoints with a root runtime
span.
- Keep raw Noise environment, registration, and stream identifiers out
of exported spans while preserving them in local debug events.
- Keep telemetry setup in a focused CLI module instead of growing the
top-level command entrypoint.

## Stack

- Previous: none (`#27058` has merged)
- Next: #27466

## Validation

- `just test -p codex-exec-server --lib` (139 passed)
- `just test -p codex-cli --test exec_server` (3 passed)
- `just bazel-lock-check`
- `just fix -p codex-exec-server -p codex-cli`
- `just fmt`

---------

Co-authored-by: Richard Lee <richardlee@openai.com>

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

@@ -13,6 +13,11 @@ pub use transport::ExecServerListenUrlParseError;
 
 use crate::ExecServerRuntimePaths;
 
+#[tracing::instrument(
+    name = "codex.exec_server",
+    skip_all,
+    fields(otel.kind = "internal")
+)]
 pub async fn run_main(
     listen_url: &str,
     runtime_paths: ExecServerRuntimePaths,