Merge branch 'slots/mail' into feat/plugin-system-audit

# Conflicts:
#	lib/__tests__/plugin-slot-catalog.test.ts

components/plugins/__tests__/fake-plugin-offer.ts

@@ -0,0 +1,43 @@
+// Test helpers: pretend a running plugin offers a frame slot, without booting
+// a sandbox. Pair with a vi.mock of '@/components/plugins/plugin-iframe-slot'
+// (FakeIframeSlot below) so the "iframe" shows the props it would receive.
+
+import React from 'react';
+import { register, deregister } from '@/lib/plugin-sandbox/registry';
+import type { ActivePlugin } from '@/lib/plugin-sandbox/registry';
+import type { SlotName } from '@/lib/plugin-types';
+
+const offered = new Set<string>();
+
+/** Registers a fake plugin that offers the given slots. */
+export function offerSlots(pluginId: string, slots: string[]): void {
+  register({
+    plugin: { id: pluginId, name: pluginId },
+    code: '',
+    tier: 'untrusted',
+    background: {},
+    slotOffers: slots.map((name) => ({ name: name as SlotName, order: 100, hasShouldShow: false })),
+    hookDisposables: [],
+  } as unknown as ActivePlugin);
+  offered.add(pluginId);
+}
+
+/** Removes every fake plugin registered with offerSlots. */
+export function clearOffers(): void {
+  for (const id of offered) deregister(id);
+  offered.clear();
+}
+
+/** Stand-in for PluginIframeSlot: a div carrying the slot name and its props as JSON. */
+export function FakeIframeSlot({ pluginId, slot, extraProps }: { pluginId: string; slot: string; extraProps?: Record<string, unknown> }) {
+  return React.createElement('div', {
+    'data-testid': `slot-${slot}`,
+    'data-plugin': pluginId,
+    'data-props': JSON.stringify(extraProps ?? {}),
+  });
+}
+
+/** The props the fake iframe of a slot received. */
+export function slotProps(el: HTMLElement): Record<string, unknown> {
+  return JSON.parse(el.getAttribute('data-props') ?? '{}');
+}