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

apps/selfhost-vm/boxes/json_adapter.nyash

@@ -0,0 +1,19 @@
+// Adapter for JSON cursor operations (extracted)
+// Wraps MiniJsonCur and exposes a stable facade
+using selfhost.vm.json_cur as MiniJsonCur
+
+static box MiniJson {
+  read_quoted_from(s, pos) {
+    local cur = new MiniJsonCur()
+    return cur.read_quoted_from(s, pos)
+  }
+  read_digits_from(s, pos) {
+    local cur = new MiniJsonCur()
+    return cur.read_digits_from(s, pos)
+  }
+  next_non_ws(s, pos) {
+    local cur = new MiniJsonCur()
+    return cur.next_non_ws(s, pos)
+  }
+}
+