fix(ui): reserve the scrollbar gutter on main scroll areas

v7 shows an 8px scrollbar that takes layout space, so a page or list
whose content crossed the overflow threshold (filtering the MCP table,
switching usage tabs) shifted every column sideways by 8px. Add a
scroll-stable utility (scrollbar-gutter: stable) and apply it to page
scroll areas, sheet bodies and the large list/table containers; menus,
code blocks and small dialogs keep the default. Drop the unused
scroll-overlay utility.

src/App.tsx

@@ -1207,7 +1207,7 @@ function App() {
       <div
         ref={providerScrollContainerRef}
         id="main-content"
-        className="min-h-0 flex-1 overflow-y-auto overflow-x-hidden px-6 pb-12 pt-4"
+        className="min-h-0 flex-1 overflow-y-auto scroll-stable overflow-x-hidden px-6 pb-12 pt-4"
       >
         <div className="space-y-4">
           {activeApp === "claude-desktop" && (
@@ -1284,7 +1284,7 @@ function App() {
                 id="main-content"
                 role="tabpanel"
                 aria-labelledby={`openclaw-config-${openclawConfigTab}`}
-                className="min-h-0 flex-1 overflow-y-auto"
+                className="min-h-0 flex-1 overflow-y-auto scroll-stable"
               >
                 {openclawConfigTab === "env" ? (
                   <EnvPanel />
@@ -1298,7 +1298,10 @@ function App() {
           );
         case "hermesMemory":
           return (
-            <div id="main-content" className="min-h-0 flex-1 overflow-y-auto">
+            <div
+              id="main-content"
+              className="min-h-0 flex-1 overflow-y-auto scroll-stable"
+            >
               <HermesMemoryPanel onOpenWebUI={openHermesWebUI} />
             </div>
           );
@@ -1350,7 +1353,10 @@ function App() {
                 </>
               }
             />
-            <div id="main-content" className="min-h-0 flex-1 overflow-y-auto">
+            <div
+              id="main-content"
+              className="min-h-0 flex-1 overflow-y-auto scroll-stable"
+            >
               <div className="px-6 pb-10 pt-4">
                 <AuthCenterPanel showIntro={false} />
               </div>

src/components/apps/AppsPage.tsx

@@ -249,7 +249,10 @@ export function AppsPage() {
         }
       />
 
-      <div id="main-content" className="min-h-0 flex-1 overflow-y-auto">
+      <div
+        id="main-content"
+        className="min-h-0 flex-1 overflow-y-auto scroll-stable"
+      >
         <div className="px-6 pb-10 pt-4">
           <div className="flex h-8 items-center px-4 text-caption font-medium text-fg-2">
             <span className="flex-1">{t("appsPage.columnApp")}</span>

src/components/common/FullScreenPanel.tsx

@@ -163,7 +163,7 @@ export const FullScreenPanel: React.FC<FullScreenPanelProps> = ({
             }
           />
 
-          <div className="flex-1 overflow-y-auto">
+          <div className="flex-1 overflow-y-auto scroll-stable">
             <div className={cn("w-full space-y-6 px-6 py-6", contentClassName)}>
               {children}
             </div>

src/components/mcp/UnifiedMcpPanel.tsx

@@ -734,7 +734,7 @@ const UnifiedMcpPanel: React.FC<UnifiedMcpPanelProps> = ({
           ) : (
             <div
               data-testid="mcp-matrix"
-              className="min-h-0 overflow-auto rounded-panel border border-border bg-surface"
+              className="min-h-0 overflow-auto scroll-stable rounded-panel border border-border bg-surface"
             >
               <MatrixColumnHighlight>
                 <div className="min-w-[560px]">
@@ -1051,7 +1051,7 @@ const UnifiedMcpPanel: React.FC<UnifiedMcpPanelProps> = ({
                 </p>
               )}
             </div>
-            <div className="flex min-h-0 flex-col gap-4 overflow-y-auto overscroll-contain">
+            <div className="flex min-h-0 flex-col gap-4 overflow-y-auto scroll-stable overscroll-contain">
               {importReport.error && (
                 <section className="flex flex-col gap-2">
                   <h3 className="m-0 text-body font-semibold">

src/components/prompts/PiNativePromptResources.tsx

@@ -134,7 +134,7 @@ function PromptDrawer({
           </SheetTitle>
           <SheetDescription className="sr-only">{description}</SheetDescription>
         </div>
-        <div className="flex min-h-0 flex-1 flex-col gap-5 overflow-y-auto overscroll-contain px-6 pb-6 pt-5">
+        <div className="flex min-h-0 flex-1 flex-col gap-5 overflow-y-auto scroll-stable overscroll-contain px-6 pb-6 pt-5">
           {children}
         </div>
         <div className="flex h-14 shrink-0 items-center gap-2 border-t border-border px-6">
@@ -907,7 +907,7 @@ export const PiPromptTemplates = forwardRef<
     return (
       <ul
         aria-label={t("pi.prompts.templatesLabel")}
-        className="m-0 min-h-0 shrink list-none overflow-y-auto rounded-panel border border-border bg-surface p-0"
+        className="m-0 min-h-0 shrink list-none overflow-y-auto scroll-stable rounded-panel border border-border bg-surface p-0"
       >
         {filteredTemplates.map((template, index) => {
           const summary = getPiPromptTemplateSummary(template.content);

src/components/prompts/PromptFormPanel.tsx

@@ -185,7 +185,7 @@ const PromptFormPanel: React.FC<PromptFormPanelProps> = ({
           </SheetDescription>
         </div>
 
-        <div className="flex min-h-0 flex-1 flex-col gap-5 overflow-y-auto overscroll-contain px-6 pb-6 pt-5">
+        <div className="flex min-h-0 flex-1 flex-col gap-5 overflow-y-auto scroll-stable overscroll-contain px-6 pb-6 pt-5">
           <div className="flex shrink-0 flex-col gap-1.5">
             <label
               htmlFor={`${baseId}-name`}

src/components/prompts/PromptLibrary.tsx

@@ -78,7 +78,7 @@ export function PromptLibrary({
   return (
     <ul
       aria-label={listLabel}
-      className="m-0 min-h-0 shrink list-none overflow-y-auto rounded-panel border border-border bg-surface p-0"
+      className="m-0 min-h-0 shrink list-none overflow-y-auto scroll-stable rounded-panel border border-border bg-surface p-0"
     >
       {filtered.map(([id, prompt], index) => {
         const summary =

src/components/providers/mode/SwitchModePanel.tsx

@@ -517,7 +517,7 @@ export function SwitchModePanel({
       <div
         ref={scrollRef}
         id="main-content"
-        className="min-h-0 flex-1 overflow-y-auto overflow-x-hidden px-6 pb-12 pt-3"
+        className="min-h-0 flex-1 overflow-y-auto scroll-stable overflow-x-hidden px-6 pb-12 pt-3"
       >
         {notices.length > 0 && (
           <div role="status" className="mb-3 flex flex-col gap-2">

src/components/sessions/SessionManagerPage.tsx

@@ -1299,7 +1299,7 @@ export function SessionManagerPage({
                   defaultValue: "会话列表",
                 })}
                 ref={listScrollRef}
-                className="mx-6 mt-3 min-h-0 shrink overflow-y-auto overscroll-contain rounded-panel border border-border bg-surface"
+                className="mx-6 mt-3 min-h-0 shrink overflow-y-auto scroll-stable overscroll-contain rounded-panel border border-border bg-surface"
                 style={{ scrollPaddingTop: groupMode === "project" ? 44 : 8 }}
               >
                 {renderList()}

src/components/sessions/reader/SessionOutline.tsx

@@ -103,7 +103,7 @@ export const SessionOutline = memo(function SessionOutline({
       </div>
       <ol
         ref={listRef}
-        className="m-0 min-h-0 flex-1 list-none overflow-y-auto overscroll-contain px-2 pb-4"
+        className="m-0 min-h-0 flex-1 list-none overflow-y-auto scroll-stable overscroll-contain px-2 pb-4"
       >
         {entries.map((entry) => {
           const active = entry.turn.index === activeTurn;

src/components/sessions/reader/SessionReader.tsx

@@ -688,7 +688,7 @@ export function SessionReader({
           const bottom = el.scrollTop + el.clientHeight >= el.scrollHeight - 24;
           setAtBottom((current) => (current === bottom ? current : bottom));
         }}
-        className="min-h-0 flex-1 overflow-y-auto overscroll-contain px-6"
+        className="min-h-0 flex-1 overflow-y-auto scroll-stable overscroll-contain px-6"
       >
         <div
           className="relative w-full"

src/components/settings/SettingsPage.tsx

@@ -381,7 +381,7 @@ export function SettingsPage({
       <div
         ref={scrollRef}
         id="main-content"
-        className="min-h-0 flex-1 overflow-y-auto"
+        className="min-h-0 flex-1 overflow-y-auto scroll-stable"
       >
         {isBusy ? (
           <div className="flex h-full items-center justify-center">

src/components/skills/SkillsPage.tsx

@@ -644,7 +644,7 @@ export function SkillsPage({
       <div className="flex min-h-0 flex-1 flex-col px-6 pb-5">
         <div
           ref={listScrollRef}
-          className="min-h-0 overflow-auto rounded-panel border border-border bg-surface"
+          className="min-h-0 overflow-auto scroll-stable rounded-panel border border-border bg-surface"
         >
           {loadingList ? (
             <div className="flex items-center justify-center gap-2 py-16 text-body text-fg-2">

src/components/skills/UnifiedSkillsPanel.tsx

@@ -1097,7 +1097,7 @@ const UnifiedSkillsPanel: React.FC<UnifiedSkillsPanelProps> = ({
     return (
       <div
         data-testid="skills-matrix"
-        className="min-h-0 overflow-auto rounded-panel border border-border bg-surface"
+        className="min-h-0 overflow-auto scroll-stable rounded-panel border border-border bg-surface"
       >
         <MatrixColumnHighlight>
           <div className="min-w-[600px]">

src/components/ui/sheet.tsx

@@ -84,7 +84,7 @@ const SheetBody = ({
 }: React.HTMLAttributes<HTMLDivElement>) => (
   <div
     className={cn(
-      "min-h-0 flex-1 overflow-y-auto overscroll-contain px-5 py-4",
+      "min-h-0 flex-1 overflow-y-auto scroll-stable overscroll-contain px-5 py-4",
       className,
     )}
     {...props}

src/components/usage/UsageDashboard.tsx

@@ -723,12 +723,12 @@ export function UsageDashboard({
       // 空库里只有定价可配：不画全是 0 的概览和趋势，直接给页签
       <div
         id="main-content"
-        className="flex min-h-0 flex-1 flex-col gap-3.5 overflow-y-auto px-6 pb-6 pt-1"
+        className="flex min-h-0 flex-1 flex-col gap-3.5 overflow-y-auto scroll-stable px-6 pb-6 pt-1"
       >
         {tabsSection}
       </div>
     ) : isEmpty ? (
-      <div className="flex min-h-0 flex-1 flex-col items-center overflow-y-auto px-6 pb-6">
+      <div className="flex min-h-0 flex-1 flex-col items-center overflow-y-auto scroll-stable px-6 pb-6">
         <div className="mt-16 flex max-w-[440px] flex-col items-center gap-3 text-center">
           <span
             aria-hidden="true"
@@ -768,7 +768,7 @@ export function UsageDashboard({
     ) : (
       <div
         id="main-content"
-        className="flex min-h-0 flex-1 flex-col gap-3.5 overflow-y-auto px-6 pb-6 pt-1"
+        className="flex min-h-0 flex-1 flex-col gap-3.5 overflow-y-auto scroll-stable px-6 pb-6 pt-1"
       >
         <UsageHero
           range={range}

src/index.css

@@ -501,11 +501,10 @@ html:not([data-keyboard]) [tabindex]:focus {
     display: none;
   }
 
-  .scroll-overlay {
-    scrollbar-gutter: stable both-edges;
-    padding-right: 0.5rem;
-    margin-right: -0.5rem;
-    overflow-x: hidden;
+  /* 滚动条常显且占 8px：主滚动区、大列表先把这条槽留出来，
+     内容高度跨过能否滚动的临界时整列不会左右横跳 */
+  .scroll-stable {
+    scrollbar-gutter: stable;
   }
 
   .border-default {