feat(teams): the public Team pages, the two slots and the nav flag

TEAMS.md §3.1–§3.5. Four core pages — the index, a Team's overview, its full
roster and the player portal's "My Teams" — plus the two extension slots a
module adds to them, and the nav rows that lead there.

These are CORE routes, not module ones. A Team is a core platform entity that a
module merely populates, so the whole experience renders on bare core; a module
adds to these pages rather than supplying them.

`team.member.row` is declared with `{ displayName, isLeader, linked }` and not
§3.4's `{ memberKey, userId, displayName }`. The two documents contradict each
other and §3.2 is the one that is a security rule: a slot component runs in the
browser, so those props can only reach it by publishing a game-internal
identifier and a site account id in every public roster response, for every
visitor, module installed or not. Recorded as an amendment.

The presentation logic is split into lib/teams.js with its own tests, following
lib/teamAdmin.js, because these pages have to state differences that read as
bugs unless they are worded deliberately:

  - "37 members · 21 linked" — the gap is information (a character with no site
    account behind it), and the header says what each number IS rather than
    showing both and hoping;
  - an empty roster has three unrelated causes — nobody in the Team, a rung
    that shows nobody, and a module that could not be asked — and reporting the
    last as the first is a statement about the game that happens to be false;
  - a stale projection says how old it is rather than presenting itself as
    current.

`teams` is the first CORE nav row to carry a `feature` since the shard rows left
with the module cutover, and it brings core's own feature provider back with it.
It gates on whether this deployment has Teams AT ALL, not on who is looking —
Team pages are public and the server gates them. It fails open, so an unknown
answer shows the link: a Teams link leading somewhere empty is a far cheaper
mistake than a Team page nobody can find.

Co-Authored-By: Claude <noreply@anthropic.com>

client/src/App.jsx

@@ -18,6 +18,9 @@ import Newsletter from './routes/public/Newsletter.jsx'
 import NewsletterIssue from './routes/public/NewsletterIssue.jsx'
 import About from './routes/public/About.jsx'
 import Status from './routes/public/Status.jsx'
+import Teams from './routes/public/Teams.jsx'
+import Team from './routes/public/Team.jsx'
+import TeamRoster from './routes/public/TeamRoster.jsx'
 import Wiki from './routes/wiki/Wiki.jsx'
 import WikiArticle from './routes/wiki/WikiArticle.jsx'
 import CmsPage from './routes/public/CmsPage.jsx'
@@ -57,6 +60,7 @@ import AcceptInvite from './routes/player/AcceptInvite.jsx'
 import PlayerPortalLayout, { PlayerIndex } from './routes/player/PlayerPortalLayout.jsx'
 import PlayerAccount from './routes/player/PlayerAccount.jsx'
 import PlayerAppeals from './routes/player/PlayerAppeals.jsx'
+import PlayerTeams from './routes/player/PlayerTeams.jsx'
 
 export default function App() {
   return (
@@ -93,6 +97,13 @@ export default function App() {
               <Route path="/site/status" element={<Status />} />
               <Route path="/wiki" element={<Wiki />} />
               <Route path="/wiki/:slug" element={<WikiArticle />} />
+              {/* Teams (TEAMS.md §3.1). Core routes, not module ones: a Team is a
+                  core platform entity that a module merely populates, so these
+                  render on bare core too. `/teams` is declared before `/:slug`
+                  below for the same reason every named route is. */}
+              <Route path="/teams" element={<Teams />} />
+              <Route path="/teams/:slug" element={<Team />} />
+              <Route path="/teams/:slug/roster" element={<TeamRoster />} />
               {/* Installed modules' public pages, namespaced `/<id>/…` — the
                   registry prefixes the segment, so a module cannot spell its way
                   out of it (docs/website/MODULE_API.md §3.3). Declared before the
@@ -216,6 +227,11 @@ export default function App() {
               <Route path="/player" element={<PlayerIndex />} />
               <Route path="/account" element={<PlayerAccount />} />
               <Route path="/account/appeals" element={<PlayerAppeals />} />
+              {/* Core's own page under the /player prefix, unlike the module
+                  pages below it. Open to any authenticated account, not role
+                  'player': staff are a superset of players and a moderator is in
+                  guilds too — RequirePlayer above already draws that line. */}
+              <Route path="/player/teams" element={<PlayerTeams />} />
               {/* Installed modules' player-portal pages, at /player/<id>/…. This
                   group's own routes are absolute (its layout route has no path),
                   so the prefix is written here rather than inherited — the one