replace analytics double-count prevention with buffer supersede

The Plug records a pageview with a known ID (plug_ref) into the ETS
buffer. When JS connects, the LiveView hook supersedes that event by
ID and records its own with full data (screen_size from connect params).
If JS never connects, the Plug's event flushes normally after 10s.

Also fixes: admin browsing no longer leaks product_view events — the
Plug now sets no analytics session data for admins, so all downstream
visitor_hash guards naturally filter them out.

Replaces the previous time-based skip logic which was brittle and
race-prone. The supersede approach is deterministic and handles both
the ETS buffer and already-flushed DB cases.

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

assets/js/app.js

@@ -591,7 +591,7 @@ const ChartTooltip = {
 
 const csrfToken = document.querySelector("meta[name='csrf-token']").getAttribute("content")
 const liveSocket = new LiveSocket("/live", Socket, {
-  params: {_csrf_token: csrfToken},
+  params: {_csrf_token: csrfToken, screen_width: window.innerWidth},
   hooks: {...colocatedHooks, ColorSync, Lightbox, CartPersist, CartDrawer, ProductImageScroll, SearchModal, CollectionFilters, CardRadioScroll, AnalyticsInit, ChartTooltip},
 })