docs/runtime: externcall + println normalization; NyRT silent result flag; PyVM console warn/error/trace routing\nselfhost(M2): add MirEmitterBox (Return(Int)->const+ret) and --emit-mir switch; initial selfhost smoke\nrunner: child args/env hardening for selfhost (NYASH_NY_COMPILER_CHILD_ARGS under --; NYASH_JSON_ONLY=1, NYASH_VM_USE_PY=1, NYASH_DISABLE_PLUGINS=1); VM path strips using lines when NYASH_ENABLE_USING=1\nmeta: clarify PyVM/llvmlite as primary (vm/interpreter legacy OFF) in CURRENT_TASK.md; README links to externcall docs

tools/test/smoke/pyvm/string_ops_basic/test.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -euo pipefail
+ROOT=$(CDPATH= cd -- "$(dirname -- "$0")/../../../../.." && pwd)
+source "$ROOT/tools/test/lib/shlib.sh"
+
+build_nyash_release
+mkdir -p "$ROOT/tmp"
+emit_json "$ROOT/apps/tests/string_ops_basic.nyash" "$ROOT/tmp/pyvm_string_ops.json"
+out=$(run_pyvm_json "$ROOT/tmp/pyvm_string_ops.json")
+echo "$out" | assert_grep '^len=5$'
+echo "$out" | assert_grep '^sub=bcd$'
+echo "$out" | assert_grep '^idx=1$'
+