feat(web): SessionDrawer + Sessions tab in AttackerDetail

Adds asciinema-player dependency, SessionDrawer.tsx that pages the
transcripts API (500 events per request) and rebuilds a v2 .cast blob
for playback, and a Session Transcripts section in AttackerDetail that
deep-links into the drawer. Truncation banner surfaces the 10 MB
per-session cap when it's been hit.

decnet_web/package.json

@@ -10,6 +10,7 @@
     "preview": "vite preview"
   },
   "dependencies": {
+    "asciinema-player": "^3.8.0",
     "axios": "^1.14.0",
     "lucide-react": "^1.7.0",
     "react": "^19.2.4",