## What changed
Parse optional `generation_id` values from image API responses and carry the selected image's ID through the image generation tool into analytics events. Keep the ID out of serialized extension items, JSON schemas, and TypeScript types. Responses without an ID remain supported.
## Testing
Add coverage for distinct IDs in multi-image responses and responses without IDs. Extend analytics and app-server tests to verify that the selected image's ID reaches analytics, and item tests to verify that it is omitted from serialization and TypeScript types.
GitOrigin-RevId: 70a600856990140b76fdbda51a0d73b3414338b1
## Why
Standalone image generation needs a typed `codex-api` client surface for
the Codex image proxy routes before the harness and model-facing tool
layers are wired in.
## What changed
- Added `ImagesClient` support for JSON `images/generations` and
`images/edits` requests.
- Added typed request and response shapes for generation, JSON edit
image URLs, image metadata, and base64 image outputs.
- Kept generation model slugs open-ended while requiring the generation
model field that the downstream endpoint expects.
- Exported the new client and image types from `codex-api`.
- Added coverage for generation and edit wire shapes, extra response
metadata that the client ignores, and malformed image responses missing
`data`.
## Validation
- `cargo test -p codex-api`
- `just fix -p codex-api`
- `just fmt`
- `git diff --check main`
Chris Dong