revert(web-shell): restore pre-#8098 composer animations at 50% opacity

packages/web-shell/client/App.module.css

@@ -719,16 +719,10 @@
    the wrapper must shrink to its content instead of filling the pane — the same
    thing `.content` already does in this state. */
 .appChatEmpty .chatViewWrap {
-  position: relative;
-  z-index: 1;
   flex: 0 0 auto;
   overflow: visible;
 }
 
-.appChatEmpty .chatPane {
-  position: relative;
-}
-
 .footer {
   position: relative;
   width: min(100%, var(--chat-shell-width));
@@ -934,18 +928,12 @@
     overflow: hidden;
   }
 
-  /* Override chatViewWrap's relative positioning so the absolute footer
-     anchors to chatPane. The wrap remains a flex item, so the z-index: 1 it
-     gets from `.appChatEmpty .chatViewWrap` still applies under static
-     positioning and keeps the welcome content and composer above the dot
-     field. The welcome-middle + custom-footer variant keeps the positioned
-     wrap: `.footerWithCustomFooter` renders `display: contents` there, so
-     the wrap must remain the containing block for `.bottomPanels`. */
+  /* The custom-footer variant renders the composer footer `display: contents`,
+     so this wrap stays the containing block for the absolutely-positioned
+     bottom panels (status panel) anchored above it. */
   .appChatEmpty
-    .chatViewWithMobileComposerBottom:not(
-      .chatViewWithWelcomeMiddle.chatViewWithCustomFooter
-    ) {
-    position: static;
+    .chatViewWithMobileComposerBottom.chatViewWithWelcomeMiddle.chatViewWithCustomFooter {
+    position: relative;
   }
 
   .appChatEmpty .chatViewWithMobileComposerBottom .footer {

packages/web-shell/client/App.test.tsx

@@ -693,12 +693,6 @@ vi.mock('./components/ChatEditor', async () => {
   };
 });
 
-vi.mock('./components/NewSessionDotField', () => ({
-  NewSessionDotField: () => (
-    <div data-web-shell-new-session-dot-field aria-hidden="true" />
-  ),
-}));
-
 vi.mock('./components/MessageList', async () => {
   const React = await import('react');
   const { useInteractionBlocker } = await import('./interactionBlockContext');
@@ -4986,9 +4980,6 @@ describe('App composer footer renderer', () => {
     expect(composer?.nextElementSibling).toBe(composerFooter);
     expect(composerFooter?.parentElement).toBe(composer?.parentElement);
     expect(composer?.parentElement?.nextElementSibling).toBe(shellFooter);
-    expect(
-      container.querySelector('[data-web-shell-new-session-dot-field]'),
-    ).toBeNull();
   });
 
   it('updates composer footer state and renders it in the empty welcome state', async () => {
@@ -5041,9 +5032,6 @@ describe('App composer footer renderer', () => {
     expect(
       container.querySelector('[data-testid="composer-footer"]'),
     ).not.toBeNull();
-    expect(
-      container.querySelector('[data-web-shell-new-session-dot-field]'),
-    ).not.toBeNull();
     expect(composerFooterProps.at(-1)).toEqual({
       disabled: false,
       isRunning: false,

packages/web-shell/client/App.tsx

@@ -104,7 +104,6 @@ import {
 } from './components/panels/EnvironmentPanel';
 import { ChatContextHeader } from './components/ChatContextHeader';
 import { WelcomeHeader } from './components/WelcomeHeader';
-import { NewSessionDotField } from './components/NewSessionDotField';
 import { ApprovalModeDialog } from './components/dialogs/ApprovalModeDialog';
 import { ResumeDialog } from './components/dialogs/ResumeDialog';
 import { DialogShell } from './components/dialogs/DialogShell';
@@ -11574,10 +11573,6 @@ export function App({
                 .filter(Boolean)
                 .join(' ')}
             >
-              {isChatEmptyState &&
-                !showMissingSessionState &&
-                !activePanel &&
-                mainView === 'chat' && <NewSessionDotField />}
               {sidebarOptions.enabled &&
                 sidebarOptions.showCompactToggle &&
                 (!chatHeaderEnabled || isChatEmptyState) &&
@@ -12069,8 +12064,9 @@ export function App({
                   hasWelcomeMiddle
                     ? styles.chatViewWithWelcomeMiddle
                     : undefined,
-                  // Marker class (no declarations): keeps the ':not(...)'
-                  // exclusion in App.module.css matching.
+                  // Positioning hook: completes the compound selector in
+                  // App.module.css that keeps this wrap relative so the
+                  // absolutely-positioned bottom panels keep their anchor.
                   CustomFooter ? styles.chatViewWithCustomFooter : undefined,
                   activePanel ||
                   mainView !== 'chat' ||
@@ -12625,7 +12621,6 @@ export function App({
                           composerInput={composerInput}
                           composerInputVersion={composerInputVersion}
                           placeholderText={composerPlaceholderText}
-                          animatePlaceholder={isChatEmptyState}
                         />
                         {CustomComposerFooter && (
                           <CustomComposerFooter