the ZIM fallback fires fast, and reads Russian in Russian (V-508)

Verification, as the task asked. Drove что такое фотосинтез through
/api/chat with the search reachable, with the container stopped, and with
the host blackholed. Kiwix claims the turn in both failure cases, and a
stopped container costs nothing: DNS fails and the ZIM answers inside the
same second.

The blackhole is the case that hurts. The search waited its full 8-second
budget before the ZIM was asked and the turn took 15.4s against 3.5, which
he sits through with nothing being said. So the connect phase alone is now
capped at 1.5s. A reachable instance that is merely slow keeps the whole
budget, because it is fanning out to real engines.

The RU Wikipedia ZIM is on the box (owner moved it into the kiwix zims
dir), and kiwix-serve picked it up. A Cyrillic question now searches
book_ru verbatim and skips the RU->EN rewrite: that rewriter is the
workaround for an English book, and against a Russian one it is a
translation of his own words back at him. Catalog names come from the
filename, not the <name> field — books.name=wikipedia_ru_all returns
nothing.

Measurement in docs/evals/2026-08-05-kiwix-offline-fallback.md. The RU book
answering a driven turn needs a rebuild and is not verified yet.

CLAUDE.md

@@ -286,6 +286,14 @@ world questions, so she needs to read external sources. What replaces it:
 - **In the world, live search leads and the ZIMs are the fallback** (owner's call,
   2026-08-02). A self-hosted SearXNG (`search` block) answers first; the Kiwix ZIMs on
   homesrv answer when the search is empty, unreachable, or the line is down.
+  **Verified with the line down on 2026-08-05** (V-508,
+  `docs/evals/2026-08-05-kiwix-offline-fallback.md`): a stopped SearXNG costs nothing,
+  the ZIM answers in the same turn budget. A blackholed host cost 8 seconds he waited
+  through. So the connect phase alone is capped at `dialTimeout` (1.5s), while a slow
+  instance that did connect keeps the full 8. **A Russian question reads
+  `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.
   `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