🐛 Preserve explicit hide-in-viewer when adding prototype interactions (#9695)

`cls/show-in-viewer` unconditionally dissoc'ed `:hide-in-viewer` on the
interaction destination, so every `add-interaction`, `add-new-interaction`,
and `update-interaction` call silently re-enabled the destination's
view-mode visibility — even when the user had just deliberately hidden
that frame. Reporter (#9049) hid a board, dragged a prototype arrow at
it, and watched the board reappear in View Mode.

Make `show-in-viewer` a no-op when the destination already has
`:hide-in-viewer true`. The auto-unhide still fires on destinations with
no explicit hide flag (the original ergonomic — new prototype targets
default to visible), but explicit user intent is now preserved across
interaction-add / interaction-update.

Behaviour change: dropping the auto-unhide on explicitly-hidden
destinations matches the reporter's expectation ("nothing would show up
in View Mode unless explicitly marked as such") and the surrounding
`:hide-in-viewer`-aware UI in `measures.cljs`, which already lets users
toggle the same property directly.

Closes #9049.

Co-authored-by: Andrey Antukh <niwi@niwi.nz>

common/src/app/common/logic/shapes.cljc

@@ -539,5 +539,12 @@
   (update shape :interactions ctsi/add-interaction interaction))
 
 (defn show-in-viewer
+  "Auto-unhide the shape in viewer when it becomes an interaction
+   destination, but only when the user has not explicitly hidden it.
+   Preserves explicit `:hide-in-viewer true` so that adding or updating
+   an interaction whose destination has been deliberately hidden does not
+   silently flip the viewer-visibility flag the user set. See #9049."
   [shape]
-  (dissoc shape :hide-in-viewer))
+  (if (true? (:hide-in-viewer shape))
+    shape
+    (dissoc shape :hide-in-viewer)))