feat(guilds): declare a second place on the guild page, for core's forum

The mirror of the activity feed, one phase later. Core owns the Team forum —
membership, manual grants and the member/guest split are all core's rules, and a
module reimplementing any of them would be reimplementing a security boundary — but
core publishes no Team page, because it does not own the word "guild". So this
module declares the place and core puts the forum in it.

TWO declarations rather than one, and that is the interesting part. A slot holds one
component and the first fill wins, so folding the forum into `uo.guild.detail`
alongside the feed would hand core the decision about where each of its two
contributions sits on a page this module owns. Separate slots also keep them
independent: with the forum switched off, the feed renders exactly as before.

The registration test now asserts the set of declared slots and that EVERY one of
them is rendered by the page that owns it, rather than naming a single slot twice.
A slot nothing renders is a slot core fills into the void.

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

client/test/registration.test.js

@@ -209,16 +209,22 @@ it('registers under exactly one module id, matching the manifest', () => {
   assert.deepEqual([...owners], [manifest.id])
 })
 
-it('declares its own guild-detail slot, for core to fill', () => {
+it('declares its own guild slots, for core to fill', () => {
   // The inverted direction (TEAMS.md Part 3). Teams are a core primitive with no
-  // core page: core owns the activity feed and this module owns the word "guild",
-  // so this module declares the place and core puts the feed in it.
-  assert.deepEqual([...registered.declaredSlots], ['uo.guild.detail'])
+  // core page: core owns the activity feed and the forum, this module owns the
+  // word "guild", so this module declares the places and core puts them in.
+  //
+  // TWO slots rather than one because a slot holds one component: stacking the
+  // feed and the forum into a single fill would take away this module's ability
+  // to place them separately on its own page.
+  assert.deepEqual([...registered.declaredSlots], ['uo.guild.detail', 'uo.guild.forum'])
 })
 
-it('the declared slot is rendered by the page that owns it', () => {
+it('every declared slot is rendered by the page that owns it', () => {
   // A slot nothing renders is a slot core fills into the void. Asserted against
   // the source rather than the chunk, since the chunk is minified.
   const page = fs.readFileSync(path.resolve(HERE, '..', 'src', 'routes', 'public', 'Guild.jsx'), 'utf8')
-  assert.match(page, /name="uo\.guild\.detail"/)
+  for (const name of registered.declaredSlots) {
+    assert.match(page, new RegExp(`name="${name.replace(/\./g, '\.')}"`))
+  }
 })