Fix CSSX colour rules: reset cssx-resolve JIT to force CEK

cssx-resolve has a complex cond with nested and conditions that the
JIT compiler miscompiles — the colour branch is skipped even when
all conditions are true. Reset to jit_failed_sentinel after loading
so it runs on CEK (which evaluates correctly).

Added vm-reset-fn kernel command for targeted JIT bypass.

All CSSX colour tokens now generate rules: text-violet-699,
text-stone-500, bg-stone-50, etc.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/bin/sx_server.ml

@@ -1008,6 +1008,18 @@ let rec dispatch env cmd =
     | Eval_error msg -> send_error msg
     | exn -> send_error (Printexc.to_string exn))
 
+  | List [Symbol "vm-reset-fn"; String name] ->
+    (* Reset a function's JIT-compiled bytecode, forcing CEK interpretation.
+       Used to work around JIT compilation bugs in specific functions. *)
+    (match Hashtbl.find_opt env.bindings name with
+     | Some (Lambda l) ->
+       l.l_compiled <- Some Sx_vm.jit_failed_sentinel;
+       Printf.eprintf "[jit] reset %s (forced CEK)\n%!" name;
+       send_ok ()
+     | _ ->
+       Printf.eprintf "[jit] reset %s: not found or not lambda\n%!" name;
+       send_ok ())
+
   | List [Symbol "aser-blob"] ->
     (* Like aser but reads source as a binary blob. *)
     let src = read_blob () in