Stable extension point for definition-form? — no monkey-patching

Replace the fragile pattern of capturing and wrapping definition-form?
with a mutable *definition-form-extensions* list in render.sx. Web
modules append names to this list instead of redefining the function.
Survives spec reloads without losing registrations.

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

web/web-forms.sx

@@ -213,27 +213,22 @@
 
 
 ;; --------------------------------------------------------------------------
-;; Patch form-classification functions
+;; Register web forms with adapters
 ;;
-;; The adapters (html, sx, dom, async) use classifier functions to decide
-;; how to handle forms during rendering. Now that these web forms are
-;; registered as custom special forms, we redefine the classifiers to
-;; include them. This runs after all adapters are loaded.
+;; Appends form names to the extension lists that definition-form?,
+;; render-html-form?, special-form? etc. check. No function wrapping —
+;; survives spec reloads.
 ;; --------------------------------------------------------------------------
 
 (define WEB_FORM_NAMES
   (list "defhandler" "defpage" "defquery" "defaction" "defrelation"))
 
-;; Redefine definition-form? to include web forms.
-;; All adapters call this to identify "eval for side effects" forms.
-(let ((core-definition-form? definition-form?))
-  (define definition-form?
-    (fn (name)
-      (or (core-definition-form? name)
-          (contains? WEB_FORM_NAMES name)))))
+;; Extend definition-form? via the stable extension point in render.sx
+(for-each (fn (name)
+  (append! *definition-form-extensions* name))
+  WEB_FORM_NAMES)
 
 ;; Extend adapter form-name lists so dispatchers recognise web forms.
-;; These lists are mutable — append! adds to them in place.
 (for-each (fn (name)
   (append! RENDER_HTML_FORMS name)
   (append! SPECIAL_FORM_NAMES name))