Group the rail's open bot with its sessions

The active row and its session previews now share one highlighted card,
with a hairline thread from the bot's icon down to the last session.

src/layouts/bots/(partials)/bot-row.tsx

@@ -27,7 +27,8 @@ type Props = {
 /**
  * 48px rail row. Status is the face and the subtitle (the bot's status
  * line while it has one): no badges, spinners or state dots.
- * Selected is ink at 5%, never a hue.
+ * The selected background (ink at 5%, never a hue) is painted by
+ * RailBotCard, which also holds the sessions.
  */
 export default function BotRow({ bot, href, selected, subtitle }: Props) {
     const hue = (bot.hue || null) as BotHue | null;
@@ -48,7 +49,7 @@ export default function BotRow({ bot, href, selected, subtitle }: Props) {
                 "flex shrink-0 h-12 items-center gap-3 rounded-default px-1 @rail:px-3 border-0 leading-normal",
                 "hover:opacity-100 hover:bg-sunken transition-colors duration-[var(--m-fast)]",
                 "focus-visible:ring-2 focus-visible:ring-ink focus-visible:ring-offset-2 focus-visible:ring-offset-paper",
-                selected && "bg-ink/5 hover:bg-ink/5",
+                selected && "hover:bg-transparent hover:dark:bg-transparent",
             )}
         >
             <BotAvatar image_media_id={bot.image_media_id} hue={hue} face={(bot.face || "idle") as BotFace} />

src/layouts/bots/(partials)/rail-bot-card.tsx

@@ -0,0 +1,25 @@
+import Stack from "@moduletrace/twui/layout/Stack";
+import type { ReactNode } from "react";
+import { twMerge } from "tailwind-merge";
+
+type Props = {
+    /**
+     * Groups the open bot's row with its sessions, so the active background
+     * covers both and the sessions read as belonging to that bot.
+     */
+    selected?: boolean;
+    children: ReactNode;
+};
+
+export default function RailBotCard({ selected, children }: Props) {
+    return (
+        <Stack
+            className={twMerge(
+                "w-full shrink-0 flex-col gap-0! items-stretch rounded-default py-1",
+                selected && "bg-ink/5",
+            )}
+        >
+            {children}
+        </Stack>
+    );
+}

src/layouts/bots/(partials)/rail-bot-entry.tsx

@@ -1,6 +1,8 @@
 import type { BotWithLastMessage } from "@/src/types";
 import BotRow from "./bot-row";
+import RailBotCard from "./rail-bot-card";
 import RailBotSessions from "./rail-bot-sessions";
+import Divider from "@moduletrace/twui/layout/Divider";
 
 type Props = {
     bot: BotWithLastMessage;
@@ -12,11 +14,24 @@ type Props = {
 /**
  * A worker in the rail, and its sessions while it is the open conversation.
  */
-export default function RailBotEntry({ bot, href, selected, workspace_id }: Props) {
+export default function RailBotEntry({
+    bot,
+    href,
+    selected,
+    workspace_id,
+}: Props) {
     return (
-        <>
+        <RailBotCard selected={selected}>
             <BotRow bot={bot} href={href} selected={selected} />
-            {selected ? <RailBotSessions key={bot.id} bot={bot} workspace_id={workspace_id} /> : null}
+            {selected ? (
+                <>
+                    <RailBotSessions
+                        key={bot.id}
+                        bot={bot}
+                        workspace_id={workspace_id}
+                    />
                 </>
+            ) : null}
+        </RailBotCard>
     );
 }

src/layouts/bots/(partials)/rail-bot-session-row.tsx

@@ -32,7 +32,7 @@ export default function RailBotSessionRow({ session, loading, disabled, onOpen }
             buttonContentProps={{ className: "w-full min-w-0 flex-nowrap" }}
             className={twMerge(
                 "w-full h-8 shrink-0 justify-start! items-center! gap-2! rounded-default px-2! @rail:pl-14! text-left text-ink dark:text-ink hover:bg-ink/5 hover:dark:bg-ink/5 focus-visible:ring-2 focus-visible:ring-ink",
-                active && "bg-sunken hover:bg-sunken hover:dark:bg-sunken opacity-100!",
+                active && "bg-transparent hover:bg-transparent hover:dark:bg-transparent opacity-100!",
             )}
         >
             <Span

src/layouts/bots/(partials)/rail-bot-sessions.tsx

@@ -30,6 +30,11 @@ export default function RailBotSessions({ bot, workspace_id }: Props) {
 
     return (
         <Stack className="hidden @rail:flex w-full shrink-0 flex-col gap-0! items-stretch pb-1">
+            <Stack className="relative w-full flex-col gap-0! items-stretch">
+                <Span
+                    aria-hidden
+                    className="pointer-events-none absolute left-7 -translate-x-1/2 -top-2 bottom-0 w-px bg-hairline"
+                />
                 {shown.map((session) => (
                     <RailBotSessionRow
                         key={session.id}
@@ -39,6 +44,7 @@ export default function RailBotSessions({ bot, workspace_id }: Props) {
                         onOpen={() => sessions.reopenSession({ session_id: Number(session.id) })}
                     />
                 ))}
+            </Stack>
             {sessions.sessions.length > AppData.RailRecentSessions ? (
                 <BotSessionsModal
                     bot={bot}

src/layouts/bots/(partials)/rail-crew-list.tsx

@@ -4,6 +4,7 @@ import { AppContext } from "@/src/pages/__root";
 import canManageCrew from "@/src/utils/rbac/can-manage-crew";
 import type { BotWithLastMessage, WorkspaceWithActivity } from "@/src/types";
 import CoordinatorRow from "./coordinator-row";
+import RailBotCard from "./rail-bot-card";
 import RailBotSessions from "./rail-bot-sessions";
 import RailBotsSection from "./rail-bots-section";
 import RailSectionAddButton from "./rail-section-add-button";
@@ -28,7 +29,7 @@ export default function RailCrewList({ bots, workspaces, selected_id }: Props) {
     return (
         <>
             {coordinator ? (
-                <>
+                <RailBotCard selected={coordinator.id === selected_id}>
                     <CoordinatorRow
                         bot={coordinator}
                         bots={bots}
@@ -37,7 +38,7 @@ export default function RailCrewList({ bots, workspaces, selected_id }: Props) {
                     {coordinator.id === selected_id ? (
                         <RailBotSessions key={coordinator.id} bot={coordinator} />
                     ) : null}
-                </>
+                </RailBotCard>
             ) : null}
             <RailBotsSection
                 action={<RailSectionAddButton title="Add a bot" onClick={() => openForm({ kind: "bot" })} />}