addItemClickHandler

Register handler for main-toolbar ToolbarAction.ItemClicked events. Clicks originating from a contextual toolbar (their ToolbarAction.ItemClicked.kind is non-null) are not forwarded — observe those with addActionListener, or veto them with addActionInterceptor. Returns a ToolbarSubscription the host must close on teardown (same lifecycle contract as addActionListener).

When to use this: same ownership rule as updateItems — call it only when you own the coordinator (Compose-only flavor or a custom host rendering its own com.pspdfkit.compose.toolbar.composables.NutrientMainToolbar). In PdfActivity / PdfFragment the SDK already registers its own click handler; handle item clicks there with com.pspdfkit.ui.PdfActivity.setOnToolbarItemClickListener instead.