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/b3_sweep.sh

@@ -14,9 +14,9 @@
 
 set -euo pipefail
 
-ROOT="${ROOT:-/home/admin/cpfs/wjh/agentic-kv}"
+ROOT="${ROOT:-$(cd "$(dirname "$0")/.." && pwd)}"
 VENV="$ROOT/.venv/bin"
-MODEL="${MODEL:-/home/admin/cpfs/wjh/models/Qwen/Qwen3-Coder-30B-A3B-Instruct}"
+MODEL="${MODEL:-$ROOT/models/Qwen/Qwen3-Coder-30B-A3B-Instruct}"
 TRACE="${TRACE:-$ROOT/traces/w600_r0.0015_st30.jsonl}"
 OUTDIR="${OUTDIR:-$ROOT/outputs/b3_sweep_$(date +%Y%m%d_%H%M%S)}"
 PROXY_PORT="${PROXY_PORT:-9300}"