imbue-mngr-codex-usage

Codex data provider for mngr usage. Codex exposes no statusline or in-process plugin, but mngr already tails its rollout JSONL into a raw transcript via mngr_codex's background-tasks supervisor. This package adds:

• The writer (codex_usage.sh): installed into the agent's commands/ dir, where mngr_codex's codex_background_tasks.sh launches it iff present. It reads the raw rollout stream and emits one cost_snapshot per token_count item to events/codex/usage/events.jsonl.
• The reader: an aggregate_usage_source hookimpl claiming the codex source, aggregated session-cumulatively (each token_count carries the session's cumulative total, so the freshest per session wins).

What gets captured

Codex reports cumulative token usage (info.total_token_usage) but no dollar cost, so cost is left null and the reader estimates it from tokens via the pricing table (provenance ESTIMATED). input_tokens includes cached, so the writer emits input = input_tokens - cached_input_tokens and cache_read = cached_input_tokens (OpenAI has no cache-write surcharge). The model is openai/<model> from the rollout's turn_context.

In ChatGPT-plan (subscription) mode, token_count also carries 5h/7d rate-limit windows, which the writer maps onto the window schema -- so Codex subscription agents get Claude-style windows, and the session is classified SUBSCRIPTION (imputed). Without rate limits it's API_KEY (real spend).