## What changed
- promote plugin config loading to an info-level `plugins_for_config`
span
- promote skill config loading to an info-level `skills_for_config` span
- attach stable OpenTelemetry names to both spans
## Why
`session_init.plugin_skill_warmup` currently combines plugin loading and
skill loading, which makes cold-start traces unable to identify which
phase dominates. These child spans preserve the existing aggregate while
making the two costs independently visible.
Context:
https://openai.slack.com/archives/C0ARA9GF5D4/p1781639496496439?thread_ts=1781202444.891669&cid=C0ARA9GF5D4
## Impact
This is observability-only. It does not change plugin or skill loading
behavior.
## Validation
- `just test -p codex-core-skills -p codex-core-plugins` (347 passed)
- `just fmt`
Matthew ZengandGitHub
2c7802e7cf