Fix island dep scanning + spread-through-reactive-if debug

deps.sx: scan island bodies for component deps (was only scanning
"component" and "macro", missing "island" type). This ensures
~cssx/tw and its dependencies are sent to the client for islands.

cssx.sx: move if inside make-spread arg so it's evaluated by
eval-expr (no reactive wrapping) instead of render-to-dom which
applies reactive-if inside island scope, converting the spread
into a fragment and losing the class attrs.

Added island dep tests at 3 levels: test-deps.sx (spec),
test_deps.py (Python), test_parity.py (ref vs fallback).

sx-browser.js: temporary debug logging at spread detection points.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/sx/ref/deps.sx

@@ -73,7 +73,7 @@
       (append! seen n)
       (let ((val (env-get env n)))
         (cond
-          (= (type-of val) "component")
+          (or (= (type-of val) "component") (= (type-of val) "island"))
             (for-each (fn ((ref :as string)) (transitive-deps-walk ref seen env))
                       (scan-refs (component-body val)))
           (= (type-of val) "macro")
@@ -105,7 +105,7 @@
     (for-each
       (fn ((name :as string))
         (let ((val (env-get env name)))
-          (when (= (type-of val) "component")
+          (when (or (= (type-of val) "component") (= (type-of val) "island"))
             (component-set-deps! val (transitive-deps name env)))))
       (env-components env))))