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>

tools/ludic-tools/ludic_syntax.h

@@ -53,22 +53,22 @@ typedef struct {
  * declaration keyword, anything stmt() dispatches on is a statement keyword. */
 static const char* LUDIC_KW_DECL[] = {
     "program","import","property","model","enum","ui",
-    "const","var","fn","extern","handler","entry", 0
+    "const","var","fn","extern","handler","entry","event","scene", 0
 };
 static const char* LUDIC_KW_CLAUSE[] = {
-    "phase","query","on", 0
+    "phase","query","on","cancellable","public","layer","start", 0
 };
 /* Documented design targets the self-hosted parser does not accept yet. Kept
  * out of the highlighted vocabulary (they would read as working keywords) until
  * they are implemented; check-vocabulary.py verifies the lists above are a
  * subset of what selfhost/parse*.ludic actually dispatches on. */
 static const char* LUDIC_KW_RESERVED[] = {
-    "scene","layer","start", 0
+    0
 };
 static const char* LUDIC_KW_STMT[] = {
     "let","return","if","else","while","for","in","spawn","despawn",
     "enable","disable","match","machine","state","become","where",
-    "and","or","not","break","continue","new", 0
+    "and","or","not","break","continue","new","emit","cancel", 0
 };
 static const char* LUDIC_TYPES[] = {
     "int","fixed","bool","entity","str","ptr","byte","words","fixeds","ptrs","void", 0