Clean up how fuzzers are laid out

test/fuzz-libghostty/src/fuzz_parser.zig

@@ -0,0 +1,15 @@
+const std = @import("std");
+const ghostty_vt = @import("ghostty-vt");
+
+pub export fn zig_fuzz_init() callconv(.c) void {
+    // Nothing to do
+}
+
+pub export fn zig_fuzz_test(
+    buf: [*]const u8,
+    len: usize,
+) callconv(.c) void {
+    var p: ghostty_vt.Parser = .init();
+    defer p.deinit();
+    for (buf[0..@intCast(len)]) |byte| _ = p.next(byte);
+}