- Add optional `max-context-length` model configuration across supported provider model types and expose it via `GetMaxContextLength`.
- Propagate the override into model metadata so Codex/client model catalog responses honor the configured value (`context_window`, `max_context_window`, and `max_context_length`).
- Update example configuration with documented usage of the new option.
Closes: #4728
- Introduced a new reasoning level, `minimal`, to the `codexClientAllowedReasoningLevels` map.
- Updated response-building logic to include descriptive messaging for the `minimal` level.
Closes: #4542
- Introduced a new `models` package for organizing Codex client model templates and building responses.
- Migrated Codex response handling to `codexmodels.BuildResponse`.
- Added comprehensive tests for model metadata, reasoning levels, and input modalities handling.
