chore: import upstream snapshot with attribution

apps/sim/blocks/visibility/client.ts

@@ -0,0 +1,70 @@
+'use client'
+
+import type { BlockVisibilityState } from '@/lib/core/config/block-visibility'
+import { notifyBlockOverlayChanged } from '@/blocks/custom/client-overlay'
+import { invalidateBlockCaches, registerBlockVisibilityResolver } from '@/blocks/visibility/context'
+
+/**
+ * Client-side visibility state, hydrated from `useBlockVisibility` by
+ * `BlockVisibilityLoader`. Registered at module load with `null` state so the
+ * very first render — including the SSR pass — is fail-closed for `preview`
+ * blocks; the post-mount fetch only ever reveals (benign pop-in) or applies a
+ * kill switch to an already-public block.
+ */
+let state: BlockVisibilityState | null = null
+
+registerBlockVisibilityResolver({ current: () => state })
+
+function setsEqual(a: Set<string>, b: Set<string>): boolean {
+  if (a.size !== b.size) return false
+  for (const value of a) if (!b.has(value)) return false
+  return true
+}
+
+function isEmptyState(vis: BlockVisibilityState): boolean {
+  return vis.revealed.size === 0 && vis.disabled.size === 0 && vis.previewTagged.size === 0
+}
+
+/**
+ * Replace the in-scope visibility state, reset registered module caches, and
+ * bump the shared block-overlay version so every subscribed consumer re-reads
+ * `getAllBlocks()`.
+ *
+ * No-ops when the change cannot alter the projection: an incoming state
+ * deep-equal to the current one (React Query refetches deliver
+ * fresh-but-identical objects on every poll — without this guard each poll
+ * would thundering-rebuild the toolbar, search, and matcher caches), or an
+ * empty state while none is set (`null` and empty are equivalent for
+ * `isHiddenUnder`, so the fail-closed reset on first mount is free).
+ */
+export function hydrateBlockVisibility(next: BlockVisibilityState): void {
+  if (state === null && isEmptyState(next)) return
+  if (
+    state &&
+    setsEqual(state.revealed, next.revealed) &&
+    setsEqual(state.disabled, next.disabled) &&
+    setsEqual(state.previewTagged, next.previewTagged)
+  ) {
+    return
+  }
+  state = next
+  invalidateBlockCaches()
+  notifyBlockOverlayChanged()
+}
+
+/**
+ * Fail-closed reset while a workspace switch's visibility fetch is in flight:
+ * preview reveals are dropped immediately (they may not apply to the new
+ * workspace), but kill-switch entries are CARRIED OVER until the new
+ * projection arrives — dropping `disabled` would flash kill-switched blocks
+ * back into discovery for the flight window, while briefly over-hiding in the
+ * new workspace is benign in both directions.
+ */
+export function resetBlockVisibilityForSwitch(): void {
+  if (state === null) return
+  hydrateBlockVisibility({
+    revealed: new Set(),
+    disabled: state.disabled,
+    previewTagged: new Set(),
+  })
+}