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/scoped.ludic

@@ -0,0 +1,21 @@
+# scoped.ludic — a despawned entity drops out of subsequent event-driven work
+# (replaces tests/mod_c/scoped_mod.c, which tested entity-scoped foreign callbacks
+# swept on despawn). Here a @On(Tick) listener counts live Units each tick; after
+# the Unit is despawned, a further tick finds none. Fires twice before the kill,
+# not the third time. Prints 2.
+program Scoped {
+  property Health { hp: int = 0 }
+  model Unit { Health }
+  var fires: int = 0
+  event Tick { }
+  @On(Tick) handler OnTick { for (Health) in query [Health, {Unit}] { fires = fires + 1 } }
+
+  entry {
+    spawn Unit { Health { hp: 1 } }
+    emit Tick()     # 1 live Unit -> fires = 1
+    emit Tick()     # fires = 2
+    for (Health) in query [Health, {Unit}] { despawn self() }   # kill the Unit
+    emit Tick()     # no live Units -> fires stays 2
+    print(fires)    # 2
+  }
+}