A title call that could not survive a model that thinks

Reported: chat names never regenerate after the first reply. They were
regenerating; the request was being made and the answer thrown away.

`complete()` returns `message.content` verbatim, and a model that emits
`<think>` inline puts its thinking in exactly the field the title is read from.
So the title came back as "<think>Okay, the user wants a short title for" --
or, once the too-long guard caught that, as the first prompt trimmed, which is
indistinguishable from titling never having run. That is what was being seen.

Underneath it, `max_tokens: 24`. Ample for six words, and nowhere near enough
for a model that reasons first: the budget goes on thinking and the content
field comes back empty or holding an unclosed tag. Too small is not a shorter
title, it is no title at all.

Both fixed: the reply goes through `reasoning.strip_reasoning`, and the budget
is `TITLE_MAX_TOKENS` with room to think. Reproduced first against the four
shapes an endpoint actually answers with -- three of them were broken -- and
the tests are written from those.

What I did *not* do is ask for a low reasoning effort on the call, which would
make it much cheaper and was the obvious move. `reasoning_effort` and
`chat_template_kwargs` appear only where somebody has opted in, so that a
provider strict about unknown parameters sees exactly the request it always
did. An LLMError here is caught and turned into a fallback title -- so a 400
would be titling silently switching itself off, which is the failure this
commit exists to fix. The token budget makes the room instead.

The shipped prompt now asks for a leading emoji, as requested. Asked for rather
than assumed: a model that ignores it gives a title without one, and an
administrator who does not want them clears the word.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/lembas/services/prompts.py

@@ -1211,13 +1211,18 @@ BUILTIN: tuple[Fragment, ...] = (
         group=GROUP_TASKS,
         order=400,
         variables=("question", "answer"),
-        hint="A separate one-message request, not part of any chat. Clear it to "
-        "stop asking a model for titles: chats are then named from their first "
-        "message, and no request is made at all.",
+        hint="A separate one-message request, not part of any chat, made once "
+        "the first reply has finished so the title can describe the exchange "
+        "rather than only the question. Clear it to stop asking a model for "
+        "titles: chats are then named from their first message, and no request "
+        "is made at all. The emoji is asked for rather than assumed — it makes "
+        "a sidebar of twenty chats scannable — and a model that ignores the "
+        "instruction simply gives a title without one.",
         default=(
-            "Summarise this exchange as a title of at most six words. Reply with the "
-            "title alone: no quotes, no punctuation at the end, no preamble. Use the "
-            "language of the exchange.\n"
+            "Summarise this exchange as a title of at most six words, beginning with "
+            "a single emoji that fits it. Reply with the title alone: no quotes, no "
+            "punctuation at the end, no preamble, no explanation. Use the language of "
+            "the exchange.\n"
             "\n"
             "User: {{question}}\n"
             "\n"