Record what Kiwix returns and why the gate is not one (V-668)

gofmt on cmd/mavwaked/silero.go came in with a99932b and blocked make test.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013ptwopxyo3Z2kwFckHkLvN

CLAUDE.md

@@ -675,11 +675,25 @@ world questions, so she needs to read external sources. What replaces it:
   `wikipedia_ru_all_maxi_2026-02` verbatim** through `kiwix.book_ru`. The RU→EN rewriter
   is the workaround for an English book and is skipped there. Kiwix catalog names come
   from the filename, not the `<name>` field.
+  **That verbatim path sent the whole sentence to a keyword engine until 09-08-2026**
+  (V-668, `docs/evals/2026-08-09-kiwix-topic-retrieval.md`). Kiwix ranks by keyword
+  overlap, so the question words outrank the one word naming the article. "что такое TCP"
+  returned "Перехват TCP-соединения". "кто написал Войну и мир" returned an episode of
+  Doctor Who. `kiwix.Topic` drops the narrative request, the interrogative and a verb
+  behind one. `kiwix.TitlePath` tries the exact article first, since a ZIM is addressable
+  by title and a wrong title is a 404. Four of eight questions reach the right article
+  where they did not, two were already right, and nothing regressed. Both apply on the
+  verbatim path alone. The rewriter already reduces a question, and reducing twice takes
+  the topic off its input.
   `Response.Empty()` is the whole gate and there is no quality threshold in front of it:
   the three signals one could read were measured on 2026-08-05 and none of them separate a
   real question from an invented one. Token overlap would cost "столица Франции" its
   answer, because the answer is Париж and that word is not in the question. See
-  `docs/evals/2026-08-05-search-quality-signals.md` (V-539). **Which query source claimed
+  `docs/evals/2026-08-05-search-quality-signals.md` (V-539). **The embedder is not a
+  fourth signal**, measured 2026-08-09 (V-668). Query-to-passage cosine scores 0.79 to
+  0.91 on answerable questions and 0.75 to 0.84 on unanswerable ones, and the sets
+  overlap. The wrong TCP article scored 0.8653, above five of six unanswerable rows. It
+  measures topic and not whether the passage answers, so no threshold splits them. **Which query source claimed
   a turn is readable on `/chat`** as a badge beside the reply, carried on
   `ipc.ChatReply.Source` and noted by `noteQuerySource` in `cmd/mavend/querysource.go`. It
   rides the context, so `handleText` keeps the one string signature the mic, telegram and