GUI read-model overhaul: server-assembled channel windows (Correct™ pagination + relay-signed bounds)

crates/buzz-core/src/kind.rs

@@ -223,6 +223,17 @@ pub const KIND_NIP29_GROUP_MEMBERS: u32 = 39002;
 /// NIP-29: Addressable group roles definition.
 pub const KIND_NIP29_GROUP_ROLES: u32 = 39003;
 
+// Channel-window overlays (relay-signed, synthesized at query time, never
+// stored). Appended to bridge `/query` responses for `top_level` window
+// requests — see docs/bridge-channel-window.md.
+/// Thread summary overlay: `e`/`d` tag = root event id, content =
+/// `{reply_count, descendant_count, last_reply_at, participants}`.
+pub const KIND_THREAD_SUMMARY: u32 = 39005;
+/// Window bounds overlay: `d` tag = `<channel_id>:<request-cursor-or-head>`,
+/// content = `{has_more, next_cursor}`. The only authority on exhaustion —
+/// clients must not infer `has_more` from row counts.
+pub const KIND_WINDOW_BOUNDS: u32 = 39006;
+
 /// Workflow definition (parameterized replaceable, d=workflow_uuid).
 pub const KIND_WORKFLOW_DEF: u32 = 30620;
 
@@ -471,6 +482,8 @@ pub const ALL_KINDS: &[u32] = &[
     KIND_NIP29_GROUP_ADMINS,
     KIND_NIP29_GROUP_MEMBERS,
     KIND_NIP29_GROUP_ROLES,
+    KIND_THREAD_SUMMARY,
+    KIND_WINDOW_BOUNDS,
     KIND_PRESENCE_UPDATE,
     KIND_TYPING_INDICATOR,
     KIND_HUDDLE_REACTION,
@@ -615,6 +628,8 @@ pub const fn is_relay_only_kind(kind: u32) -> bool {
             | KIND_PRESENCE_SNAPSHOT
             | KIND_MESH_LLM_RELAY_STATUS
             | KIND_DM_VISIBILITY
+            | KIND_THREAD_SUMMARY
+            | KIND_WINDOW_BOUNDS
     )
 }
 
@@ -639,6 +654,8 @@ const _: () = assert!(is_parameterized_replaceable(KIND_WORKFLOW_DEF)); // 30620
 const _: () = assert!(is_parameterized_replaceable(KIND_EVENT_REMINDER)); // 30300 ∈ 30000–39999
 const _: () = assert!(is_parameterized_replaceable(KIND_MESH_LLM_RELAY_STATUS)); // 30621 ∈ 30000–39999
 const _: () = assert!(is_parameterized_replaceable(KIND_DM_VISIBILITY)); // 30622 ∈ 30000–39999
+const _: () = assert!(is_parameterized_replaceable(KIND_THREAD_SUMMARY)); // 39005 ∈ 30000–39999
+const _: () = assert!(is_parameterized_replaceable(KIND_WINDOW_BOUNDS)); // 39006 ∈ 30000–39999
 
 // Compile-time: NIP-34 parameterized replaceable kinds are in the correct range.
 const _: () = assert!(

crates/buzz-db/src/lib.rs

@@ -1243,23 +1243,21 @@ impl Db {
         thread::get_thread_summary(&self.pool, community_id, event_id).await
     }
 
-    /// Top-level messages for a channel.
-    pub async fn get_channel_messages_top_level(
+    /// One channel window: top-level rows + summaries + server `has_more`.
+    pub async fn get_channel_window(
         &self,
         community_id: CommunityId,
         channel_id: Uuid,
         limit: u32,
-        before_cursor: Option<DateTime<Utc>>,
-        since_cursor: Option<DateTime<Utc>>,
+        cursor: Option<(DateTime<Utc>, Vec<u8>)>,
         kind_filter: Option<&[u32]>,
-    ) -> Result<Vec<thread::TopLevelMessage>> {
-        thread::get_channel_messages_top_level(
+    ) -> Result<thread::ChannelWindow> {
+        thread::get_channel_window(
             &self.pool,
             community_id,
             channel_id,
             limit,
-            before_cursor,
-            since_cursor,
+            cursor,
             kind_filter,
         )
         .await

crates/buzz-db/src/migration.rs

@@ -698,7 +698,7 @@ mod tests {
 
         run_migrations(&pool).await.expect("run migrations");
 
-        assert_eq!(applied_versions(&pool).await, vec![1, 2]);
+        assert_eq!(applied_versions(&pool).await, vec![1, 2, 3]);
         let sql = migration_sql();
         let tables = create_tables(sql.as_str());
         for table in [