fix(coach): scroll the Coach with the same scrollbar as every other surface

src/app/coach/conversations/page.tsx

@@ -17,7 +17,6 @@ import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import { PageHeader } from "@/components/ui/page-header";
 import { QueryErrorCard } from "@/components/ui/query-error-card";
-import { COACH_SCROLLBAR } from "@/components/insights/coach-panel/message-thread";
 import { ConversationRename } from "@/components/insights/coach-panel/conversation-rename";
 import { ConversationTranscript } from "@/components/insights/coach-panel/conversation-transcript";
 import {
@@ -170,7 +169,6 @@ function CoachConversationsBody({ readOnly }: { readOnly: boolean }) {
         data-slot="coach-conversations-list"
         className={cn(
           "-mx-1 flex min-h-0 flex-1 flex-col gap-4 overflow-y-auto px-1",
-          COACH_SCROLLBAR,
         )}
       >
         {isLoading && visible.length === 0 ? (

src/app/coach/plans/page.tsx

@@ -17,7 +17,6 @@ import { PageHeader } from "@/components/ui/page-header";
 import { QueryErrorCard } from "@/components/ui/query-error-card";
 import { EmptyState } from "@/components/ui/empty-state";
 import { Skeleton } from "@/components/ui/skeleton";
-import { COACH_SCROLLBAR } from "@/components/insights/coach-panel/message-thread";
 import {
   useCoachPlans,
   useCoachPlanMutations,
@@ -238,7 +237,6 @@ function CoachPlansBody({ readOnly }: { readOnly: boolean }) {
         data-slot="coach-plans-list"
         className={cn(
           "-mx-1 flex min-h-0 flex-1 flex-col gap-4 overflow-y-auto px-1",
-          COACH_SCROLLBAR,
         )}
       >
         {query.isError ? (

src/components/insights/coach-panel/coach-input.tsx

@@ -383,7 +383,6 @@ export function CoachInput({
             "order-1 w-full min-w-0 flex-1 resize-none bg-transparent text-base leading-relaxed outline-none sm:pointer-fine:text-sm",
             "px-2 py-1.5",
             "max-h-[9.5rem] overflow-auto",
-            "[scrollbar-width:thin] [scrollbar-color:color-mix(in_srgb,var(--primary)_35%,transparent)_transparent]",
             "placeholder:text-muted-foreground aria-disabled:opacity-60",
             "placeholder:overflow-hidden placeholder:text-ellipsis placeholder:whitespace-nowrap",
           )}

src/components/insights/coach-panel/history-rail.tsx

@@ -25,7 +25,6 @@ import { useLoadMoreSentinel } from "@/hooks/use-load-more-sentinel";
 import type { CoachConversationDTO } from "@/lib/ai/coach/types";
 import { groupConversationsByRecency } from "@/lib/insights/coach-conversation-groups";
 
-import { COACH_SCROLLBAR } from "./message-thread";
 import { ConversationRename } from "./conversation-rename";
 import {
   useCoachConversationHistory,
@@ -153,7 +152,6 @@ export function HistoryRail({
           // `pb-20` keeps the last row clear of the panel's floating New
           // chat button; it pads this list's own scroll area, not `main`.
           "-mx-1 flex min-h-0 flex-1 flex-col gap-3 overflow-y-auto overscroll-contain px-1 pb-20",
-          COACH_SCROLLBAR,
         )}
       >
         {isLoading && visible.length === 0 ? (

src/components/insights/coach-panel/message-thread.tsx

@@ -365,28 +365,6 @@ export function placeInterleaved(
   return { before, beforeOptimistic, tail };
 }
 
-/**
- * v1.18.7 — shared thin/rounded/subtle scrollbar styling for the Coach
- * scroll regions (the message thread + the history list). Kept as a
- * Tailwind-arbitrary class string so the styling is component-scoped —
- * the parallel agent owns `globals.css` and we must not touch it.
- *
- * Firefox: `scrollbar-width: thin` + a tinted thumb on a transparent
- * track. WebKit: an 8 px overlay-style thumb with a fully rounded
- * radius and no arrow buttons, brightening on hover. The Dracula purple
- * is mixed down so the bar reads as a hairline accent, not a hard edge.
- */
-export const COACH_SCROLLBAR = cn(
-  "[scrollbar-color:color-mix(in_srgb,var(--primary)_30%,transparent)_transparent] [scrollbar-width:thin]",
-  "[&::-webkit-scrollbar]:w-2 [&::-webkit-scrollbar]:h-2",
-  "[&::-webkit-scrollbar-track]:bg-transparent",
-  "[&::-webkit-scrollbar-button]:hidden [&::-webkit-scrollbar-button]:size-0",
-  "[&::-webkit-scrollbar-thumb]:rounded-full",
-  "[&::-webkit-scrollbar-thumb]:border-[3px] [&::-webkit-scrollbar-thumb]:border-transparent [&::-webkit-scrollbar-thumb]:bg-clip-content",
-  "[&::-webkit-scrollbar-thumb]:bg-[color-mix(in_srgb,var(--primary)_30%,transparent)]",
-  "hover:[&::-webkit-scrollbar-thumb]:bg-[color-mix(in_srgb,var(--primary)_45%,transparent)]",
-);
-
 /**
  * The wrapper every assistant turn renders in, streaming or persisted, so a
  * turn keeps one element through the swap. While it streams it is the live
@@ -686,10 +664,6 @@ export function MessageThread({
             // the cap only bites on the wide page surface.
             "[&>*]:mx-auto [&>*]:w-full [&>*]:max-w-2xl",
             "scroll-smooth",
-            // v1.18.7 — thin, rounded, subtle scrollbar (WebKit + Firefox),
-            // component-scoped via Tailwind arbitrary variants so globals.css
-            // stays untouched. Replaces the default boxy/angular track.
-            COACH_SCROLLBAR,
           )}
         >
           {[