Actually substitute token array. init_language_core.

Seems like perf improved

core_lexing.cpp

@@ -209,6 +209,7 @@ lex_add_token(Core_Ctx *ctx, Token *token) {
   Token *top = (Token *)arena_push_size(ctx->stage_arena, sizeof(Token));
   *top = *token;
   ctx->tokens.len += 1;
+  ctx->tokens.cap += 1;
   ctx->tokens.data = (Token *)ctx->stage_arena->memory.data;
 }