New POST /knowledge/entities/synthesize-merge { source_id,
target_id } that calls the local Ollama with both entities' names
+ descriptions and returns a synthesized merged-description draft.
Read-only on the database — the curation UI uses the response as
the editable seed in the merge picker; the actual merge still
requires a follow-up PATCH-target-description + POST /merge.
The handler drops the KnowledgeDao lock before the LLM call so
other knowledge reads aren't blocked while generation runs
(typically seconds). Failure mode is 503 with an explicit hint
that the UI should fall back to skip-synthesis — keeps the merge
action working when the model is offline.
Output is lightly cleaned (leading "Merged description:" /
surrounding quotes stripped) since small models reach for those
patterns even with explicit "no preamble" guidance. Heavier
parsing isn't worth it — the curator edits anyway.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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