## Why
`log_remote_compact_failure` was the only consumer of the
compact-request logging payload and most of the token-usage breakdown
fields. Once that failure log is removed, keeping the surrounding
carrier types leaves dead plumbing in the compaction path and context
manager.
## What changed
- Remove `log_remote_compact_failure`, `CompactRequestLogData`, and the
v2 wrapper that only fed that log.
- Let both remote compaction implementations return the original
compaction error directly.
- Replace `TotalTokenUsageBreakdown` with a narrow helper that returns
only the remaining value needed by compaction analytics.
- Keep `estimate_response_item_model_visible_bytes` private to the
context manager implementation.
## Validation
- `cargo check -p codex-core`
pakrym-oai
08cb633c06