test(web): keyless e2e — OTLP collector receives the session ledger

Boot the real dsh web tree against an in-test OTLP/HTTP collector and a
mock LLM server, drive one turn over /api, then SIGINT. Asserts the wire:
OTLP JSON structure and resource identity, both instrumentation scopes,
ledger event coverage in seq order, prompt fidelity in the exported body,
the first-of-step chunk projection, and the ops shutdown marker arriving
through the exit drain.

apps/cli/package.json

@@ -124,7 +124,9 @@
     "js-yaml": "^4.2.0"
   },
   "devDependencies": {
+    "@deepseek-ai/dsh-llm-mock-server": "workspace:^",
     "@types/js-yaml": "^4.0.9",
+    "execa": "^10.0.0",
     "node-pty": "1.1.0"
   }
 }