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/net_rt.ludic

@@ -0,0 +1,33 @@
+# net_rt.ludic — a blessed, server-authoritative replication runtime (NETWORKING
+# N6). It ties the language's networking primitives together into a batteries-
+# included default, the way tests/mod_c/mod.c proved the event ABI — but written
+# in Ludic, over the built-in transport, with no foreign code.
+#
+# This is LIBRARY POLICY, not the language (NETWORKING-DESIGN §10, §12): it picks
+# server-authoritative state replication. The seams stay open — swap this for
+# lockstep+rollback (world_save + tick_fixed on misprediction) or your own.
+#
+# Frame layout on the wire: [i32 entity id][synced field bytes]. The authority
+# calls rt_replicate(e) per entity each tick; a peer calls rt_receive() to drain
+# inbound snapshots and apply them. serialize/apply are the compiler-generated
+# @Sync codecs; net_send/net_poll are the transport seam (built-in loopback here,
+# a real socket when a program binds `extern fn net_send/net_poll`).
+
+# The authority ships one entity's authoritative synced state to peers.
+fn rt_replicate(e: int) -> void {
+  let w = words(512)
+  w[0] = e                                 # entity id in the first word
+  let n = serialize(e, offset(w, 4))       # synced fields after it
+  net_send(0, w, 4 + n)
+}
+
+# A peer drains every inbound snapshot and applies it to the named entity. One
+# datagram per poll (the transport is datagram-preserving), so loop until empty.
+fn rt_receive() -> void {
+  let w = words(512)
+  var n = net_poll(w, 2048)
+  while n > 0 {
+    apply(w[0], offset(w, 4), n - 4)        # w[0] = entity id; bytes follow
+    n = net_poll(w, 2048)
+  }
+}