fix(events): staff could not reach their own participation history

Found by the live walk, signed in as an admin: /account/events redirected to
the dashboard. `GET /player/events/history` is behind requireAuth alone and
self-scoped on req.user.id -- staff are a superset of players -- but the WEB
has two logged-in shells, and RequirePlayer sends anyone who is not a
`player` out of /account. A single mount there is a screen the reviewing
admin can never open.

Engagement Phase 7 hit this exact wall with the inbox and answered it with
two routes, one pair of components and one mapping. `eventHistoryPath` joins
`inboxPath` and `notificationSettingsPath` in notificationPaths.js rather
than starting a second file with the same comment at the top of it. The
staff path is /admin/events/mine, in the Events section of the sidebar, and
it is the one row in that group with no `roles`.

Also: the eventAnnounce fixture carried no slug, state or `listed`, so
`eventUrl` answered undefined in every test in that file and the new code
was exercised by none of them. The fixture now looks like a definition row,
and three tests cover the link, the unlisted case and the draft case.

The run.failed assertion that came with them was reading the wrong layer:
`baseFor` assembles eventUrl for every trigger and the SEAM drops the keys a
trigger does not declare, so the declaration test is what proves it. Removed,
with a note saying where the rule actually lives.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016wDDVXWMDz82WqE1i969r4

client/src/routes/admin/AdminLayout.jsx

@@ -142,6 +142,12 @@ export const NAV = [
       // governs: what a deployment permits at all is configuration, not a read,
       // and the server gates both the GET and the PUT on `admin`.
       { to: '/admin/events/actions', label: 'Actions', icon: IconGear, roles: ['admin'] },
+      // Phase 14a, and the one row here that is not about running the
+      // deployment: it is this staff member's OWN attendance, the same screen
+      // and the same route a player reads at /account/events. It has no `roles`
+      // because it needs none — every account has a participation history, and
+      // the server scopes it to the caller.
+      { to: '/admin/events/mine', label: 'My participation', icon: IconCalendar },
     ],
   },
   {
@@ -229,6 +235,7 @@ const TITLES = {
   '/admin/events': 'Events',
   '/admin/events/calendar': 'Event calendar',
   '/admin/events/actions': 'Event actions',
+  '/admin/events/mine': 'My participation',
   '/admin/events/new': 'New event',
 }