embedding nv2

docs/embedding/NV2_IMPLEMENTATION_NOTES.md

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+# NV2 - Embedding persistence and job orchestration
+
+This patch continues the new parallel `at.procon.dip.embedding.*` subsystem introduced in NV1.
+
+## Scope
+
+NV2 adds:
+
+- representation-driven selection policy
+- `DOC.doc_embedding_job` queue table
+- job lifecycle service with retry scheduling
+- model-catalog sync into `DOC.doc_embedding_model`
+- persistence of vectors into `DOC.doc_embedding`
+- orchestrator for enqueueing and processing jobs
+- unit tests for the new orchestration layer
+
+## Still intentionally missing
+
+- no cutover of the old vectorization route
+- no scheduler / background polling by default
+- no semantic search engine yet
+- no migration / backfill yet
+
+## Intended usage
+
+New code can now do:
+
+1. enqueue a document or representation for embedding with a configured model key
+2. process the pending jobs through the new provider-based subsystem
+3. store the resulting vectors in the generic DOC embedding tables
+
+## Next step after NV2
+
+NV3 should add:
+
+- `PgVectorSemanticSearchEngine`
+- semantic repository
+- query embedding integration into the generic search engine
+- hybrid lexical + semantic fusion