Networking N2–N6, and a fully C-free toolchain

Implement the rest of NETWORKING-DESIGN.md (N2–N6) and eliminate every
`.c` file from the repo. clang remains only the LLVM-IR assembler; no C
is compiled anywhere.

Networking (selfhost/emit_net.ludic + parser/emit changes):
- N2 @Sync: per-model serialize/apply + by-kind dispatchers; POD-scalar
  compile error and empty-participation warning; selective replication.
- N3 @Owned: @L_owner array + owner/set_owner/is_owner; owners snapshot.
- N4 @ToServer/@ToClients remote events: framed net_send + net_pump re-emit.
- N5 @Server/@Predicted role guards + drivable sim (tick_fixed/tick_render,
  entry-owns-the-loop).
- Built-in loopback transport so multiplayer runs with zero foreign code;
  extern fn net_send/net_poll still overrides it for a real socket.
- N6 blessed runtime (examples/net_rt.ludic) + end-to-end demo (net_demo).
- Fix: llty("entity") is now i32 (entities are i32 handles), so let e = self().

C elimination:
- Networking + foreign-mod-ABI tests rewritten as self-contained pure-Ludic
  programs (examples/net_*, world_*, mod_events, scoped); tests/ removed.
- Reflection ABI exposed to Ludic as world_* builtins (Ludic-to-Ludic modding).
- Formatter rewritten C→Ludic: tools/ludic-tools/fmt.ludic.
- Language server rewritten C→Ludic: tools/ludic-tools/lsp.ludic (lexer, index
  parser, cross-file workspace resolver, JSON, all LSP handlers).
- Obsolete migrate_*.c codemods deleted; ludic_syntax.h kept as vocabulary data.

Suites: ./test.sh 44/44, ./tools/test-tools.sh 28/28 (LSP 42/42), fixpoint holds.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

selfhost/emit_machine.ludic

@@ -26,14 +26,26 @@ fn emit_machine(st: Node) -> void {
   nmach = nmach - 1
 }
 
+# `become Name` — a machine state transition when Name is a state of an
+# enclosing `machine`, otherwise a scene transition. A scene transition runs the
+# source scene's on-exit, stores the target scene id into @L_scene, and runs the
+# target's on-enter (two direct calls and a store — no dispatch table).
 fn emit_become(st: Node) -> void {
-  if nmach == 0 { perr("'become' outside a machine") }
-  let m = mach_stk[nmach - 1]
-  var target: Node = null
-  var i = 0
-  while i < len(m.kids) { if (m.kids[i].s == st.s) { target = m.kids[i] };  i = i + 1 }
-  if (target == null) { perr(`become: no state {st.s}`) }
-  let regv = emit_expr(m.a)
-  let sv = emit_expr(target.b)
-  emit("  call void @fn_rt_set_reg(i32 ");  emit(regv.code);  emit(", i32 ");  emit(sv.code);  emit(")\n")
+  if nmach > 0 {                                        # inside a machine: try a state first
+    let m = mach_stk[nmach - 1]
+    var target: Node = null
+    var i = 0
+    while i < len(m.kids) { if (m.kids[i].s == st.s) { target = m.kids[i] };  i = i + 1 }
+    if (target != null) {
+      let regv = emit_expr(m.a)
+      let sv = emit_expr(target.b)
+      emit("  call void @fn_rt_set_reg(i32 ");  emit(regv.code);  emit(", i32 ");  emit(sv.code);  emit(")\n")
+      return
+    }
+  }
+  let sc = find_scene(st.s)                             # else a scene transition
+  if (sc == null) { perr(`become: no state or scene {st.s}`) }
+  if (g_cur_scene != null) { emit("  call void @scene_exit_");  emit(g_cur_scene.s);  emit("()\n") }
+  emit("  store i32 ");  emit(itoa(sc.ival));  emit(", ptr @L_scene\n")
+  emit("  call void @scene_enter_");  emit(sc.s);  emit("()\n")
 }