logiguard fork: GPUI xdg-activation keyboard-focus serial fix

Single-commit orphan branch: full zed-industries/zed @ 8c74db0 source tree
with a 3-file patch applied (no upstream history).

Patch (crates/gpui_linux/src/linux/wayland/):
  - serial.rs: add SerialKind::KeyboardEnter
  - client.rs: store wl_keyboard.enter serial; add latest_serial_of()
  - window.rs: activate() uses keyboard-enter serial (Mutter focus gate)

Mutter honors window activation only when the token carries the keyboard-
focus serial from wl_keyboard.enter; GPUI used a stale mouse-press serial.
See docs/tray-window-focus-wayland.md in logiguard.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/collab/src/db/tables/buffer.rs

@@ -0,0 +1,48 @@
+use crate::db::{BufferId, ChannelId};
+use sea_orm::entity::prelude::*;
+
+#[derive(Clone, Debug, PartialEq, Eq, DeriveEntityModel)]
+#[sea_orm(table_name = "buffers")]
+pub struct Model {
+    #[sea_orm(primary_key)]
+    pub id: BufferId,
+    pub epoch: i32,
+    pub channel_id: ChannelId,
+    pub latest_operation_epoch: Option<i32>,
+    pub latest_operation_lamport_timestamp: Option<i32>,
+    pub latest_operation_replica_id: Option<i32>,
+}
+
+#[derive(Copy, Clone, Debug, EnumIter, DeriveRelation)]
+pub enum Relation {
+    #[sea_orm(has_many = "super::buffer_operation::Entity")]
+    Operations,
+    #[sea_orm(has_many = "super::buffer_snapshot::Entity")]
+    Snapshots,
+    #[sea_orm(
+        belongs_to = "super::channel::Entity",
+        from = "Column::ChannelId",
+        to = "super::channel::Column::Id"
+    )]
+    Channel,
+}
+
+impl Related<super::buffer_operation::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Operations.def()
+    }
+}
+
+impl Related<super::buffer_snapshot::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Snapshots.def()
+    }
+}
+
+impl Related<super::channel::Entity> for Entity {
+    fn to() -> RelationDef {
+        Relation::Channel.def()
+    }
+}
+
+impl ActiveModelBehavior for ActiveModel {}