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_owner.ludic

@@ -0,0 +1,25 @@
+# net_owner.ludic — N3: entity ownership (NETWORKING-DESIGN §6.3, §13 N3).
+#
+# `@Owned` gives a model an owner slot (the @L_owner array). owner(e) reads it,
+# set_owner(e, id) assigns it (the authority does), is_owner(e) tests it against
+# the local peer id. Ownership gates who may write @Sync(to: owner) fields and who
+# runs @Predicted handlers; it is part of the world snapshot, so it round-trips
+# through rollback/replication. A fresh entity is unowned (-1). This assigns and
+# tests ownership against the default local id (0). Prints -1 / 7 / 0 / 1.
+program NetOwner {
+  @Sync property Pos { x: int = 0, y: int = 0 }
+  @Owned model Unit { @Sync Pos }
+
+  entry {
+    spawn Unit { Pos { x: 5, y: 6 } }
+    for (Pos) in query [Pos, {Unit}] {
+      let e = self()
+      print(owner(e))                     # -1 — fresh entity is unowned
+      set_owner(e, 7)
+      print(owner(e))                     # 7  — the authority assigned it
+      print(is_owner(e))                  # 0  — local id 0 != 7
+      set_owner(e, 0)
+      print(is_owner(e))                  # 1  — now the local peer owns it
+    }
+  }
+}