[bug] wiki_refine_draft with only a draft_id stamps synth_model and writes a refined_llm memo #583

What happened

wiki_refine_draft (mcp_server/handlers/wiki_refine.py::handler_refine) accepts a call carrying nothing but draft_id. title, lead, sections and frontmatter are all optional and update_draft skips every field that is None, but synth_model defaults to claude_refine_v1 and is always passed, so the update touches a row, returns updated: true, and insert_memo writes a refined_llm row into wiki.memos.

A call that refines nothing therefore leaves an audit trail saying a model refined the draft, and stamps the draft's synth_model with a model that did not write its content. Since #579 the tool is registered, so any MCP client can make that call.

Found by the review of PR #581 (#581 (comment)). The behavior predates that PR; exposing the tool is what makes it reachable.

Expected behavior

A refinement carries content. When title, lead, sections and frontmatter are all absent, the handler returns an error naming what it expects and writes nothing: no synth_model, no memo.

Evidence required to close

A test that calls the handler with only a draft_id and asserts the draft row and wiki.memos are both unchanged, and that the response is an error.