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/lib/notificationPaths.js

@@ -19,3 +19,17 @@ export const inboxPath = (user) => (isStaff(user) ? '/admin/notifications' : '/a
 /** The per-channel preferences screen. */
 export const notificationSettingsPath = (user) =>
   isStaff(user) ? '/admin/notifications/settings' : '/account/notifications/settings'
+
+/**
+ * This account's own event participation (events Phase 14a).
+ *
+ * The third screen to need this mapping, and it needed it for exactly the reason
+ * the two above did: `GET /player/events/history` is behind `requireAuth` alone,
+ * self-scoped on `req.user.id` — a staff member has a participation history like
+ * anyone else, and the group's own header says staff are a superset of players.
+ * The WEB is what disagrees, because `RequirePlayer` sends them to the login
+ * page. Found the same way the notifications pair was: signed in as an admin,
+ * the screen simply redirected.
+ */
+export const eventHistoryPath = (user) =>
+  isStaff(user) ? '/admin/events/mine' : '/account/events'