Register dmChannelMeta schema and dm-channel-meta HyperDB collection.

Defines structured storage for DM sidebar previews and readByUserJson
to support Phase 656 dm-meta materialization.

Co-authored-by: Cursor <[email protected]>

build.js

@@ -259,6 +259,24 @@ ns.register({
   ]
 })
 
+ns.register({
+  name: 'dmChannelMeta',
+  compact: true,
+  fields: [
+    { name: 'channelId', type: 'string', required: true },
+    { name: 'isGroup', type: 'bool' },
+    { name: 'peerUserId', type: 'string' },
+    { name: 'displayName', type: 'string' },
+    { name: 'participantIdsJson', type: 'string' },
+    { name: 'lastMessageAt', type: 'uint' },
+    { name: 'lastMessagePreview', type: 'string' },
+    { name: 'lastMessageAuthorId', type: 'string' },
+    { name: 'lastMessageHasAttachment', type: 'bool' },
+    { name: 'lastMessageHasSticker', type: 'bool' },
+    { name: 'readByUserJson', type: 'string' }
+  ]
+})
+
 Hyperschema.toDisk(schema)
 
 const db = HyperDB.from(SCHEMA_DIR, DB_DIR)
@@ -344,6 +362,11 @@ pdb.collections.register({
   schema: '@pearcord/attachment',
   key: ['id']
 })
+pdb.collections.register({
+  name: 'dm-channel-meta',
+  schema: '@pearcord/dmChannelMeta',
+  key: ['channelId']
+})
 
 pdb.indexes.register({
   name: 'messages-by-channel-time',