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/world_spawn.ludic

@@ -0,0 +1,20 @@
+# world_spawn.ludic — EV2b reflection: a mod creates a fresh entity by model id
+# (replaces tests/mod_c/world_spawn.c). world_spawn reuses the compiler's own
+# spawn lowering (alloc, kind, component defaults, @OnSpawn), so a mod-spawned
+# entity is indistinguishable from one born in source. Prints 1 / 42 / 1.
+program WorldSpawn {
+  property Health { hp: int = 0, max: int = 0 }
+  model Unit { Health }
+  @Public @OnSpawn(Unit) handler Init { }          # world table; leave defaults
+
+  entry {
+    let Um = world_model_id("Unit")
+    let e  = world_spawn(Um)                        # the mod creates an entity
+    let H  = world_prop_id("Health")
+    let hp = world_field_id(H, "hp")
+    print(world_has(e, H))          # 1 — spawn attached Health with defaults
+    world_set(e, H, hp, 42)
+    print(world_get(e, H, hp))      # 42
+    print(world_count())            # 1 — it is really in the world
+  }
+}