feat(guilds): name the core contribution each declared slot wants

Core no longer fills a slot by name - it offers a contribution and the module
that owns the page says where each one goes (MODULE_API 1.6.0, amended). The
three slot names are unchanged and stay this module's own vocabulary; what is
new is the second argument saying which of core's three contributions belongs
in each place.

Nothing here worked differently before. The change is for every game that is
not this one: core used to fill the literal name uo.guild.detail, so a second
module declaring a place under its own id got an empty page and no error.

The registration fake gained the same validation core does, including the
contribution catalogue - written down rather than imported, since this suite
runs against the built chunk with no core in the process, which makes it a
claim about core that has to be re-read when core's list changes.

42 client tests, 437 server tests.

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

client/src/entry.jsx

@@ -189,10 +189,13 @@ registry.registerExtension(ID, 'player.invite.accepted', InviteGameAccountStep)
 // populates, but core does not own the word "guild" and publishes no Team page of
 // its own — so the page is ours and core contributes the activity feed to it.
 //
-// Declared under this module's own namespace, which core enforces. Core's fill is
-// applied after every module chunk has evaluated, so declaring it here is early
-// enough; on a core that knows nothing of Teams it simply stays empty.
-registry.declareModuleSlot(ID, 'uo.guild.detail')
+// Declared under this module's own namespace, which core enforces. The second
+// argument is what gets core's content into the place: **core offers a
+// CONTRIBUTION and never names a slot**, so this module says where each one goes
+// and keeps its own word for the place. Core's fills are applied after every
+// module chunk has evaluated, so declaring here is early enough; on a core that
+// knows nothing of Teams the slot simply stays empty.
+registry.declareModuleSlot(ID, 'uo.guild.detail', { core: 'team.activity' })
 
 // A SECOND place on the same page, for core's Team forum (TEAMS.md Part 5). Two
 // declarations rather than one, because a slot holds one component and this module
@@ -200,14 +203,14 @@ registry.declareModuleSlot(ID, 'uo.guild.detail')
 // the feed reads as part of the guild's story, the forum is a room you go into.
 // Neither knows the other exists, and a core that fills only one leaves the other
 // empty.
-registry.declareModuleSlot(ID, 'uo.guild.forum')
+registry.declareModuleSlot(ID, 'uo.guild.forum', { core: 'team.forum' })
 
 // And a THIRD, at the top of the same page, for core's per-Team notification
 // control (TEAMS.md §6.3). Same reasoning as the other two and a different place:
 // muting a guild is an action ON this page, so it sits with the page's heading
 // rather than after its content. Core resolves whether this viewer is in the
 // Team at all — this module neither knows nor asks.
-registry.declareModuleSlot(ID, 'uo.guild.header')
+registry.declareModuleSlot(ID, 'uo.guild.header', { core: 'team.notify' })
 
 // `module.json`'s `coreApi` range is checked by the loader before this file is
 // ever served, so there is nothing to re-check here. It is logged because a