Fix review bugs: PD-sep counter leaks, hardcoded paths, missing deps

Critical:
- cache_aware_proxy: _handle_pd_sep leaked p_inst.num_requests (never
  decremented) and never managed d_inst.num_requests; fix media_type
  from application/json to text/event-stream for SSE stream

High:
- b3_sweep/b3_isolated_policy/b3_analyze: replace hardcoded
  /home/admin/cpfs/wjh/ ROOT with script-relative $(dirname "$0")/..
- b3_analyze: replace hardcoded 8-port WORKER_MAP with dynamic
  generation from BASE_PORT and N_INSTANCES

Medium:
- analyze_breakdown: warn on stderr when records are skipped (was silent)
- deploy_vllm_patches: fail-fast on SSH/SCP errors instead of
  continuing with empty VENV_SITE
- pyproject.toml: declare fastapi and uvicorn as runtime dependencies
- launch_elastic_p2p: kill EngineCore and proxy in trap handler to
  prevent GPU memory leaks on exit

scripts/analyze_breakdown.py

@@ -12,9 +12,11 @@ else:
 print("Total records: %d" % len(data))
 
 results = []
+skipped = 0
 for d in data:
     keys = ["t_proxy_recv", "t_prefill_sent", "t_prefill_done", "t_decode_sent", "t_first_token"]
     if not all(k in d for k in keys):
+        skipped += 1
         continue
     results.append({
         "input": d["input_length"],
@@ -26,6 +28,9 @@ for d in data:
 
 results.sort(key=lambda x: x["input"])
 print("Complete breakdown: %d" % len(results))
+if skipped:
+    print("WARNING: %d records skipped (missing breakdown timestamps)" % skipped,
+          file=sys.stderr)
 
 if not results:
     print("No complete records yet")