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_decl.ludic

@@ -70,21 +70,32 @@ fn emit_program() -> void {
   g_uses_str = false
   g_uses_intstr = false
   g_uses_strslice = false
+  g_uses_loopback = false
   loc_name = new []ptr;  loc_reg = new []ptr;  loc_ty = new []ptr;  loc_mut = new []int
   brk_lbl = new []ptr;   cnt_lbl = new []ptr
   self_stk = new []ptr
   mach_stk = new []Node
   emit_header()
+  emit_extern_decls()
   if has_ecs() { emit_ecs_storage() }
   var i = 0
   while i < len(prog) { if prog[i].kind == N_FN { emit_fn(prog[i]) };  i = i + 1 }
+  if len(g_events) > 0 { emit_event_fns() }       # EV0: @ev_<E> event-dispatch functions
+  if has_ecs() and len(g_events) > 0 { emit_world_table() }   # EV2: the mod reflection ABI
   if has_ecs() { emit_ecs_allocator();  emit_snapshot() }
+  if has_ecs() { emit_net() }                     # N2/N3: @Sync serializers + @Owned storage (gated internally)
   if has_ui() { emit_ui_build() }
-  if has_systems() { emit_game_main() }
-  else {
+  if has_systems() and has_entry() {              # N5: game owns its loop via `entry`
+    emit_game_defs()                              # system fns, hooks, tick helpers
     i = 0
     while i < len(prog) { if prog[i].kind == N_MAIN { emit_main(prog[i]) };  i = i + 1 }
   }
+  else { if has_systems() { emit_game_main() }    # the auto frame loop
+  else {
+    i = 0
+    while i < len(prog) { if prog[i].kind == N_MAIN { emit_main(prog[i]) };  i = i + 1 }
+  } }
+  if g_uses_loopback { emit_loopback() }         # built-in transport, after all net_send/net_poll uses are seen
   if g_uses_str { emit_str_prelude() }          # @fn_str_eq / @fn_str_concat, after all uses are seen
   if g_uses_intstr { emit_int_str() }           # @fn_int_str, for str(int) in interpolation
   if g_uses_strslice { emit_str_slice() }       # @fn_str_slice, for s[a..b]