animation strip

src/lib/utils/url-state.ts

@@ -6,6 +6,11 @@
  * Writes use `replaceState` rather than `goto`, so mirroring state never adds a
  * history entry or re-runs a load - the back button still means "the page
  * before", not "the previous day I clicked".
+ *
+ * Callers must pass the URL *untracked* (`get(page).url`, not `$page.url`).
+ * Reading it reactively inside the same effect that writes it creates a loop:
+ * replaceState publishes a new URL, the effect re-runs, writes again - which
+ * Svelte eventually kills with `effect_update_depth_exceeded`, hanging the page.
  */
 import { browser } from '$app/environment';
 import { replaceState } from '$app/navigation';