feat(lang): L8 registries by declaration - registry and def

registry NAME of RECORD [as PREFIX] is a global table; def NAME key { ... } in
any file is one entry, collected in source order and filled before any code
runs. Each entry gets an index constant (PREFIX_KEY), the table PREFIX_COUNT,
and a record with a key field gets it filled and a NAME_find(key). A record
literal naming a field its record lacks is now an error everywhere; a global's
initializer is lowered as its own file's code (its errors, and what its module
may see, were whichever statement came last).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

selfhost/backend/emit_head.ludic

@@ -68,6 +68,10 @@ function emit_global_init_fn() -> void {
   while i < len(prog) {
     let d = prog[i]
     if d.kind == N_VAR and global_needs_init_code(d) {
+      # an initializer is the global's own file's code: its errors, and what its module
+      # may see (L3), are that file's - not whichever statement was lowered last
+      g_err_file = d.file
+      g_err_line = d.line
       let v = emit_expr(d.a)
       let cv = coerce_code(v, d.ty)                 # any conversion is its own line, before the store
       emit("  store ");  emit(llty(d.ty));  emit(" ");  emit(cv);  emit(", ptr @g_");  emit(d.s);  emit("\n")