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/tests/macro/if/assign_join_basic.nyash

@@ -0,0 +1,5 @@
+function main(args) {
+  local a = 0
+  if 1 { a = 1 } else { a = 2 }
+}
+

apps/tests/macro/if/assign_three_vars.nyash

@@ -0,0 +1,17 @@
+function main(args) {
+  local a, b, c
+  local d = 1
+  if d == 1 {
+    a = 1
+    b = 2
+    c = 3
+  } else {
+    a = 10
+    b = 20
+    c = 30
+  }
+  print(a)
+  print(b)
+  print(c)
+}
+

apps/tests/macro/if/assign_two_vars.nyash

@@ -0,0 +1,15 @@
+function main(args) {
+  local x, y
+  local c = 1
+  if c == 1 {
+    x = 10
+    y = 20
+  } else {
+    x = 30
+    y = 40
+  }
+  // ensure use
+  print(x)
+  print(y)
+}
+

apps/tests/macro/if/then_only.nyash

@@ -0,0 +1,8 @@
+function main(args) {
+  local x = 0
+  if 1 {
+    x = 42
+    print(x)
+  }
+}
+

apps/tests/macro/if/with_else.nyash

@@ -0,0 +1,11 @@
+function main(args) {
+  local x
+  local c = 0
+  if c == 1 {
+    x = 10
+  } else {
+    x = 20
+  }
+  print(x)
+}
+