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>

examples/scenes.ludic

@@ -1,9 +1,19 @@
-# ⚠️ NOT YET IMPLEMENTED by the self-hosted compiler. `scene` / `layer` /
-# `on enter` / `on exit` have no parser support today, so this file does NOT
-# compile with build/ludicc — it is a design sketch of the intended syntax (see
-# LANGUAGE.md §"Scenes & layers"). It is deliberately excluded from test.sh.
-# Games that need scene-like states use a mode register + `machine` today, as
-# examples/chronorift does.
+# scenes — one active scene at a time, each grouping handlers into layers behind
+# an implicit active-scene register (see LANGUAGE.md §"Scenes & layers").
+#
+# Running it (feed a few keystrokes so the loop ticks) prints:
+#   1000 1 101 102 2 3 900 201 900 202 900
+#     1000     Boot (a global handler) runs once at Start
+#     1        Title is `start`; its `on enter` fires at boot
+#     101      frame 1 Update: only Title.Main.Tick runs (Play is not active)
+#     102      frame 2 Update: Tick reaches 2 -> `become Play`…
+#     2 3      …which runs Title's `on exit` then Play's `on enter`
+#     900      Play renders the same frame it is entered (Hud.Draw)
+#     201 900  frame 3: Play.World.Step, then Hud.Draw
+#     202 900  frame 4: Step reaches 2 -> quit(); Hud.Draw paints the last frame
+#
+#   ./selfhost/game-build.sh build/ludicc examples/scenes.ludic /tmp/scenes
+#   printf 'aaaa' | /tmp/scenes
 program SceneDemo {
   const R_N: int = 0