added: profiling toolchain (py-spy, pyinstrument, pytest-benchmark, memray, snakeviz)

New `profile` optional-deps group, opt-in Pyinstrument ASGI middleware
gated by DECNET_PROFILE_REQUESTS, bench marker + tests/perf/ micro-benchmarks
for repository hot paths, and scripts/profile/ helpers for py-spy/cProfile/memray.

scripts/profile/cprofile-cli.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# Run a `decnet` subcommand under cProfile and write a .prof file for snakeviz.
+# Usage: scripts/profile/cprofile-cli.sh services
+#        scripts/profile/cprofile-cli.sh status
+set -euo pipefail
+
+if [[ $# -lt 1 ]]; then
+    echo "Usage: $0 <decnet-subcommand> [args...]" >&2
+    exit 1
+fi
+
+OUT="${OUT:-profiles/cprofile-$(date +%s).prof}"
+mkdir -p "$(dirname "$OUT")"
+
+python -m cProfile -o "${OUT}" -m decnet.cli "$@"
+echo "Wrote ${OUT}"
+echo "View with: snakeviz ${OUT}"