Waiting plugin toasts now give way to the same plugin's newer ones

What

A toast is a small pop-up notification. Plugins, which are add-ons that extend Claude Code, can show them. This release changes how a plugin's toasts line up and replace one another.

• Plugin toasts now carry a per-plugin key and two ordering settings, waitsItsTurn and invalidates, when toasts are not stacked. Before, the key was plugin-toast-${...} and there were no ordering settings.
• A plugin toast that is still waiting to be shown gives way to that plugin's newer toasts, so the older one is dropped without ever appearing. A debug note records this.
• New helpers manage a stack of toasts. They cap how many toasts the stack can hold and log any toast that leaves the stack before it was drawn.
• Toast and status text now passes through a sanitizer, a step that cleans up text before it is shown.

Why

When a plugin sends several notifications in a row, you now see its latest one instead of a backlog of out-of-date ones. Plugin authors should expect toasts that were queued and then replaced to never appear.