Task-by-task TDD plan implementing the LanceDB design spec: dependency
swap, the PaperlessLanceVectorStore adapter, atomic merge_insert upsert,
ANN threshold + scalar index + compaction, the indexing/chat/similar
rewires, FAISS migration, and a lazy-import guard test so non-AI paths
(management commands) never drag in llama_index/lancedb/pyarrow.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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