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/libs/test_assert.nyash

@@ -0,0 +1,16 @@
+// TestAssertBox: tiny assertions for scripts
+static box TestAssertBox {
+  assert_eq(actual, expected, msg) {
+    if actual == expected { return true }
+    print("[ASSERT_EQ FAIL] " + msg)
+    print("  expected: " + expected)
+    print("  actual  : " + actual)
+    return false
+  }
+  assert_true(cond, msg) {
+    if cond { return true }
+    print("[ASSERT_TRUE FAIL] " + msg)
+    return false
+  }
+}
+