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>

selfhost/ast.ludic

@@ -17,6 +17,18 @@ const N_EXTERN: int = 11
 const N_UI:     int = 12
 const N_ENUM:   int = 27         # enum Name { A, B, ... } — named int constants
 const S_TOGGLE: int = 28         # enable/disable  (ival: 1=enable 0=disable; s=target; a=entity or null)
+const N_SCENE:  int = 45         # scene Name [start] { on enter{} on exit{} layer L { handlers } }
+                                 #   s=name  ival=scene id  a=on-enter block  b=on-exit block
+const S_ATTACH: int = 46         # attach P on e [{ overrides }]  — add a property to a live entity
+                                 #   s=property  a=entity expr  b=override record (E_REC) or null
+const S_DETACH: int = 47         # detach P on e  — remove a property from a live entity
+                                 #   s=property  a=entity expr
+const N_EVENT:  int = 48         # event Name { field: T = default, ... } — a public event payload
+                                 #   s=name  kids=payload fields (N_FIELD)
+const S_EMIT:   int = 49         # emit E(field: v, ...) — fire event E (calls its @On listeners)
+                                 #   s=event name  a=E_REC of named args; also usable as an
+                                 #   expression (a cancellable event returns its cancelled flag)
+const S_CANCEL: int = 50         # cancel — inside a listener, veto a `cancellable` event
 # statements
 const S_LET:      int = 10
 const S_ASSIGN:   int = 11