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_analyze.sh

@@ -9,11 +9,19 @@
 
 set -euo pipefail
 
-ROOT="${ROOT:-/home/admin/cpfs/wjh/agentic-kv}"
+ROOT="${ROOT:-$(cd "$(dirname "$0")/.." && pwd)}"
 VENV="$ROOT/.venv/bin"
 SWEEP_DIR="${1:?usage: $0 <sweep_dir>}"
 
-WORKER_MAP="http://127.0.0.1:8000=engine_0,http://127.0.0.1:8001=engine_1,http://127.0.0.1:8002=engine_2,http://127.0.0.1:8003=engine_3,http://127.0.0.1:8004=engine_4,http://127.0.0.1:8005=engine_5,http://127.0.0.1:8006=engine_6,http://127.0.0.1:8007=engine_7"
+BASE_PORT="${BASE_PORT:-8000}"
+N_INSTANCES="${N_INSTANCES:-8}"
+
+# Build WORKER_MAP dynamically from BASE_PORT and N_INSTANCES.
+_worker_map_parts=()
+for ((i=0; i<N_INSTANCES; i++)); do
+    _worker_map_parts+=("http://127.0.0.1:$((BASE_PORT + i))=engine_$i")
+done
+WORKER_MAP=$(IFS=,; echo "${_worker_map_parts[*]}")
 
 _has_engine_data() {
     # Return 0 (true) if $1/*.jsonl contains any non-empty file.