fix: nombre de archivo .md usa topic del output, no del session pre-cacheado

El session dict se obtiene antes de generator.generate() y puede
contener datos de la sesión anterior. Ahora se extrae el topic
directamente de la línea "Topic:" del header del output generado,
que siempre refleja la sesión actual usada en la generación.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/bot/bot.py

@@ -341,6 +341,7 @@ async def cmd_generate(update: Update, ctx: ContextTypes.DEFAULT_TYPE):
         # Send as file if very long
         if len(output) > 8000:
             import tempfile
+            import re as _re
             ext_map = {
                 OutputType.PODCAST: "script.md",
                 OutputType.BLOG: "post.md",
@@ -350,7 +351,11 @@ async def cmd_generate(update: Update, ctx: ContextTypes.DEFAULT_TYPE):
                 OutputType.BLOG_EXTENDED: "blog_extended.md",
                 OutputType.PODCAST_EXTENDED: "script_extended.md",
             }
-            filename = f"researchowl_{session['topic'][:30].replace(' ', '_')}_{ext_map[output_type]}"
+            # Use the topic from the output header (written at generation time)
+            # instead of the pre-fetched session dict which may be stale.
+            _m = _re.search(r'^Topic:\s*(.+)$', output[:500], _re.MULTILINE)
+            _topic = _m.group(1).strip() if _m else session["topic"]
+            filename = f"researchowl_{_topic[:30].replace(' ', '_')}_{ext_map[output_type]}"
 
             with tempfile.NamedTemporaryFile(mode="w", suffix=".md", delete=False) as f:
                 f.write(output)