pyvm: split op handlers into ops_core/ops_box/ops_ctrl; add ops_flow + intrinsic; delegate vm.py without behavior change

net-plugin: modularize constants (consts.rs) and sockets (sockets.rs); remove legacy commented socket code; fix unused imports
mir: move instruction unit tests to tests/mir_instruction_unit.rs (file lean-up); no semantic changes
runner/pyvm: ensure using pre-strip; misc docs updates

Build: cargo build ok; legacy cfg warnings remain as before

tools/test/smoke/macro/string_indexof_output_smoke.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+root=$(cd "$(dirname "$0")"/../../../.. && pwd)
+bin="$root/target/release/nyash"
+src="apps/tests/macro/strings/index_of_demo.nyash"
+
+if [ ! -x "$bin" ]; then
+  echo "nyash binary not found at $bin; build first (cargo build --release)" >&2
+  exit 1
+fi
+
+out=$("$bin" --backend vm "$root/$src" 2>/dev/null)
+test "$out" = "6" || { echo "[FAIL] expected 6, got '$out'" >&2; exit 2; }
+echo "[OK] string indexOf output passed"
+exit 0
+