review fixes: version bump, keyword check, warning assertion

Fixes from subagent review:
- ASDF version 0.3.0 → 0.4.0
- define-preset now checks (check-type name keyword) at macro-expand time
- load-preset-unknown-warns test now uses (signals warning ...) to
  actually verify the warning fires (was false-positive before)

src/components/theme.lisp

@@ -22,6 +22,7 @@
 (defmacro define-preset (name &key dark light)
   "Define a theme preset with DARK and LIGHT variants.
 NAME should be a keyword (e.g., :default, :nord)."
+  (check-type name keyword)
   `(setf (gethash ,name *presets*) '(:dark ,dark :light ,light)))
 
 (defun load-preset (theme preset-name)