Cover ChunkBbox construction and serialization, ChunkBboxResponse camelCase output, rechunk endpoint bbox propagation, and frontend store test data alignment with the new bboxes field.
Chunk/ChunkingOptions types, rechunkAnalysis API, store actions (currentChunks, rechunk), ChunkPanel UI, Prepare tab in StudioPage gated by chunking feature flag, i18n keys (FR/EN), and tests.