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/layer_events.ludic

@@ -0,0 +1,27 @@
+# layer_events.ludic — EV1 for layers + SCENES E2 (layer toggle). A `public` layer
+# promotes its show/hide to events; `enable layer L` / `disable layer L` flips the
+# layer on and off (its handlers stop running while hidden) and fires
+# layer_<L>_show / layer_<L>_hide. This closes the last scope of "events across the
+# whole architecture" — properties, models, scenes, program, and now layers.
+#
+# Running it prints:  50 2 1 50
+program LayerEvents {
+  var step: int = 0
+
+  @On(layer_Hud_show) handler Shown  { print(1) }   # a mod reacts when the HUD returns
+  @On(layer_Hud_hide) handler Hidden { print(2) }   # ...and when it's hidden
+
+  scene Main start {
+    layer Hud public {
+      handler Draw phase Update { print(50) }        # only runs while Hud is enabled
+    }
+    layer Ctrl {
+      handler Drive phase LateUpdate {
+        step = step + 1
+        if step == 1 { disable layer Hud }           # frame 1: hide -> Hidden 2, Draw stops
+        if step == 2 { enable layer Hud }            # frame 2: show -> Shown 1, Draw resumes
+        if step == 3 { quit() }                      # frame 3: after Draw ran again
+      }
+    }
+  }
+}