Persistent Lisp image for sx_eval: smart file reload + IO tracing

sx_eval now accepts files (smart-loaded by mtime — unchanged files skip),
trace_io (harness-wrapped IO capture), mock (evaluated platform overrides),
and setup params. Definitions survive between calls. sx_harness_eval also
uses smart loading. sx_write_file can create new files.

New lib/hyperscript/debug.sx: mock DOM platform for instant hyperscript
testing — compile and execute HS expressions against simulated elements,
see every DOM mutation and wait in the IO trace.

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

lib/hyperscript/debug.sx

@@ -0,0 +1,38 @@
+;; Hyperscript debug harness — mock DOM for instant testing
+;;
+;; Load once into the image, then repeatedly call hs-run.
+;; All DOM ops are intercepted and logged via the test harness.
+
+;; ── Mock element ────────────────────────────────────────────────
+
+(define
+  hs-mock-element
+  (fn
+    (tag id classes)
+    (let
+      ((cls-set (reduce (fn (d c) (dict-set d c true)) {} classes)))
+      {:children () :_hs-activated true :tag tag :classes cls-set :text "" :id id :attrs {}})))
+
+;; ── Mock platform ───────────────────────────────────────────────
+
+(define hs-mock-platform {:hs-wait (fn (ms) nil) :hs-wait-for (fn (target event) nil) :dom-get-attr (fn (el attr) (get (get el "attrs") attr)) :dom-has-class? (fn (el cls) (dict-has? (get el "classes") cls)) :dom-set-text (fn (el text) (dict-set! el "text" text) nil) :hs-settle (fn (el) nil) :dom-add-class (fn (el cls) (dict-set! (get el "classes") cls true) nil) :dom-query (fn (sel) nil) :dom-remove-class (fn (el cls) (dict-delete! (get el "classes") cls) nil) :dom-listen (fn (target event-name handler) (handler {:target target :type event-name})) :dom-set-attr (fn (el attr val) (dict-set! (get el "attrs") attr val) nil) :dom-query-all (fn (sel) ())})
+
+;; ── Convenience runner ──────────────────────────────────────────
+
+(define
+  hs-run
+  (fn
+    (src)
+    (let
+      ((me (hs-mock-element "div" "test" ()))
+        (sx (hs-to-sx-from-source src)))
+      (let
+        ((handler (eval-expr (list (quote fn) (quote (me)) (list (quote let) (quote ((it nil) (event {:target me :type "click"}))) sx)))))
+        (handler me)
+        me))))
+
+;; ── Element inspection ──────────────────────────────────────────
+
+(define hs-classes (fn (el) (keys (get el "classes"))))
+
+(define hs-has-class? (fn (el cls) (dict-has? (get el "classes") cls)))