fix(observabilidade): close DB no SIGTERM e distinguir ENOENT/parse errors

api/routes/sessions.ts

@@ -46,7 +46,18 @@ export function createSessionsRouter(db: SessionsDb): Router {
       const { events } = await parseSessionFile(session.jsonl_path)
       return res.json({ meta: session, events })
     } catch (err) {
-      return res.status(500).json({ error: 'Failed to parse session', message: (err as Error).message })
+      const e = err as NodeJS.ErrnoException
+      if (e.code === 'ENOENT') {
+        return res.status(410).json({
+          error: 'Session file missing (stale index)',
+          session_id: parsed.data.id,
+        })
+      }
+      const isProduction = process.env.NODE_ENV === 'production'
+      return res.status(500).json({
+        error: 'Failed to parse session',
+        ...(isProduction ? {} : { message: e.message }),
+      })
     }
   })