feat(bot): answer treatment questions from the clinical-guideline knowledge base

- menu button «Вопрос о лечении» -> kb.question -> rag.answer (KR quote + source)
  or «уточните у врача»; dose questions get a fixed doctor redirect
- free text in idle that looks like a question (no check-in signals, not a drug
  question) -> knowledge base; no answer -> the usual support phrase
- routing order unchanged: consent/safety first, side effects/quit/alcohol -> check-in,
  own drug -> med_qa (instruction only, SPEC §7 p.5)
- question cues, small talk and texts in config/texts/knowledge.yaml; scrub placeholders
  before "что такое X" no longer hide the definition question

Refs #64

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/dialog/flows/knowledge.py

@@ -0,0 +1,102 @@
+"""Questions about the condition and its treatment → knowledge base of clinical guidelines (#64, RAG #60).
+
+    menu «Вопрос о лечении» ──▶ kb.question (free text) ──▶ rag.answer: KR quote + source, or «уточните у врача»
+    free text in idle that looks like a question (veteran_daily `text:idle`, after the check-in signals and the
+        drug question) ──▶ rag.answer, or the usual support phrase when the KB has no answer
+
+The engine has already scrubbed the text, checked consent and run the safety check (ACUTE never gets here).
+Questions about the patient's own drug stay with `med_qa` (instruction only, SPEC §7 п.5); this flow answers
+general questions from the guidelines, extractively and without doses (`app.llm.rag.qa`). Logs carry codes only.
+"""
+
+import logging
+import re
+from functools import lru_cache
+from pathlib import Path
+
+import yaml
+from pydantic import BaseModel, ConfigDict
+
+from app.config import get_settings
+from app.dialog.contracts import Event, Reply
+from app.dialog.flows.core import menu_reply
+from app.dialog.fsm import Ctx, Step, abandonable, handler_for, state, trigger
+from app.llm import rag
+from app.llm.med_qa import DOSE_QUESTION
+
+log = logging.getLogger(__name__)
+
+QUESTION_STATE = "kb.question"
+# `scrub()` placeholders and the punctuation around them: "[NAME], что такое ПТСР?" starts with "что такое".
+_PLACEHOLDERS = re.compile(r"^(?:\s*\[[A-Z_]+\][\s,.:;!-]*)+")
+
+
+class KnowledgeTexts(BaseModel):
+    model_config = ConfigDict(extra="forbid", frozen=True)
+
+    prompt: str
+    dose_redirect: str
+    question_starts: list[str]
+    small_talk: list[str]
+
+
+@lru_cache
+def load_knowledge_texts(path: Path | None = None) -> KnowledgeTexts:
+    path = path or get_settings().config_dir / "texts" / "knowledge.yaml"
+    return KnowledgeTexts.model_validate(yaml.safe_load(path.read_text(encoding="utf-8")))
+
+
+@lru_cache
+def _question_start() -> re.Pattern[str]:
+    starts = sorted(load_knowledge_texts().question_starts, key=len, reverse=True)
+    return re.compile(r"^\s*(?:" + "|".join(re.escape(s) for s in starts) + r")\b", re.IGNORECASE)
+
+
+@lru_cache
+def _small_talk() -> re.Pattern[str]:
+    return re.compile(r"\b(?:" + "|".join(re.escape(s) for s in load_knowledge_texts().small_talk) + r")\b", re.I)
+
+
+def looks_like_question(text: str) -> bool:
+    """A "?" anywhere or a question word at the start ("что такое флэшбек", "можно ли ..."); small talk
+    ("как дела?") is not a question for the knowledge base."""
+    text = _PLACEHOLDERS.sub("", text)
+    if _small_talk().search(text):
+        return False
+    return "?" in text or bool(_question_start().search(text))
+
+
+async def knowledge_answer(ctx: Ctx, *, explicit: bool) -> str | None:
+    """KB answer for `ctx.text`. No answer → «уточните у врача» if the patient asked via the menu (`explicit`),
+    `None` otherwise (the caller keeps its own reply, e.g. the support phrase)."""
+    if ctx.text is None:
+        return None
+    if DOSE_QUESTION.search(ctx.text.lower()):
+        log.info("kb: dose question redirected to doctor")
+        return load_knowledge_texts().dose_redirect
+    reply = await rag.answer(ctx.text, audience="patient")
+    if reply is not None:
+        log.info("kb: answered docs=%s", ",".join(c.doc for c in reply.citations))
+        return reply.text
+    log.info("kb: no answer explicit=%s", explicit)
+    return rag.fallback_text("patient") if explicit else None
+
+
+@trigger("button:menu:kb_question")
+async def _menu_question(ctx: Ctx, event: Event) -> Step:
+    return Step(replies=[Reply(text=load_knowledge_texts().prompt)], next_state=QUESTION_STATE)
+
+
+@state(QUESTION_STATE)
+async def _question(ctx: Ctx, event: Event) -> Step:
+    if event.type != "text" or ctx.text is None:
+        # A menu button or a reminder instead of the question: drop the question and let idle handle it.
+        step = Step(next_state="idle")
+        idle = handler_for("idle")
+        return step.then(await idle(ctx, event)) if idle is not None else step
+    text = await knowledge_answer(ctx, explicit=True)
+    return Step(replies=[menu_reply(ctx, text)], next_state="idle")
+
+
+# A question asked yesterday must not swallow today's message.
+abandonable("kb")