feat(harness): derive a 3-5 keyword session name (YAKE, no LLM)

New sessions get a concise Italian-keyword `name` instead of the truncated
question. `tht session new` (when no --name is given) derives it via a new
`_extract_name` helper using YAKE (pure-Python, unsupervised, Italian, no LLM),
dropping generic query verbs and keeping the top keywords in reading order;
falls back to `_summarize` if YAKE is unavailable. `create_session` core keeps
its `name=None` default — the policy lives at the CLI layer.

TDD: tests/test_session_name.py (unit + CliRunner integration). Full harness
suite 269 passed; ruff clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

harness/tht/session/store.py

@@ -3,6 +3,8 @@ import shutil
 from datetime import UTC, datetime
 from pathlib import Path
 
+import yake
+
 from tht.config import DatabaseConfig
 from tht.session.models import SessionManifest
 from tht.textutil import slugify
@@ -10,6 +12,17 @@ from tht.textutil import slugify
 MANIFEST = "session_manifest.yaml"
 MAX_SLUG_CHARS = 40
 MAX_SUMMARY_CHARS = 120
+MAX_NAME_CHARS = 60
+MAX_NAME_WORDS = 5
+
+# Generic query verbs/words dropped from a derived session name (lowercased compare);
+# they carry no content and would just crowd out the salient keywords.
+_STOPNAME = {
+    "crea", "creare", "elenca", "elencare", "elencami", "mostra", "mostrami", "mostrare",
+    "dammi", "dai", "trova", "trovami", "cerca", "cercami", "voglio", "vorrei", "fammi",
+    "quanti", "quante", "quanto", "quanta", "conta", "numero", "lista", "elenco", "vedi",
+    "visualizza", "ottieni", "restituisci", "calcola", "esponi", "riporta", "fornisci",
+}
 
 
 class SessionError(Exception):
@@ -29,6 +42,37 @@ def _summarize(question: str) -> str:
     return first[:MAX_SUMMARY_CHARS]
 
 
+def _extract_name(question: str) -> str:
+    """Nome-sintesi (3-5 parole-chiave) della domanda per la sidebar, senza LLM (YAKE).
+
+    Le parole-chiave restano nella lingua della domanda (è contenuto, non chrome UI).
+    Ripiega su `_summarize` se YAKE non è disponibile o non estrae nulla di utile."""
+    q = (question or "").strip()
+    if not q:
+        return ""
+    try:
+        extractor = yake.KeywordExtractor(lan="it", n=1, top=8, dedupLim=0.9)
+        ranked = [k for k, _ in extractor.extract_keywords(q)]
+    except Exception:
+        return _summarize(question)
+    seen: set[str] = set()
+    picked: list[str] = []
+    for k in ranked:
+        kl = k.lower()
+        if kl in _STOPNAME or kl in seen:
+            continue
+        seen.add(kl)
+        picked.append(k)
+        if len(picked) >= MAX_NAME_WORDS:
+            break
+    if not picked:
+        return _summarize(question)
+    ql = q.lower()
+    picked.sort(key=lambda k: ql.find(k.lower()))  # natural reading order
+    name = " ".join(picked)
+    return (name[0].upper() + name[1:])[:MAX_NAME_CHARS]
+
+
 def render_question_md(question: str, assumptions: list[str] | None = None) -> str:
     """Rende question.md in modo deterministico: domanda + assunzioni opzionali.