fix: keep first work preview full height during teacher welcomes

src/pages/Chat/CodingChatPanel.tsx

@@ -794,7 +794,7 @@ export function CodingChatPanel({
           onToggleConsultation={() => setConsultationOpen((current) => !current)}
           projectName={activeProject?.name}
           consultationOpen={consultationOpen}
-          teacherEntry={activeProject ? <TeacherCompanion companion={teacherCompanion} open={consultationOpen} onOpen={openTeacher} onToggle={toggleTeacher} bubbleRef={setTeacherBubble} introductionRef={setTeacherIntroduction} /> : undefined}
+          teacherEntry={activeProject ? <TeacherCompanion companion={teacherCompanion} open={consultationOpen} onOpen={openTeacher} onToggle={toggleTeacher} bubbleRef={setTeacherBubble} introductionRef={setTeacherIntroduction} showWelcomes={!agentBrowserOpen} /> : undefined}
         />
 
         <div className="classroom-workspace-toolbar" data-testid="classroom-workspace-toolbar">

src/pages/Chat/TeacherCompanion.tsx

@@ -6,13 +6,15 @@ import { TeacherIntroduction } from './TeacherIntroduction';
 import type { useTeacherCompanion } from './use-teacher-companion';
 
 type Companion = ReturnType<typeof useTeacherCompanion>;
-export function TeacherCompanion({ companion, open, onOpen, onToggle, bubbleRef, introductionRef }: {
+export function TeacherCompanion({ companion, open, onOpen, onToggle, bubbleRef, introductionRef, showWelcomes = true }: {
   companion: Companion;
   open: boolean;
   onOpen(agentId?: string): void;
   onToggle?(agentId?: string): void;
   bubbleRef?: Ref<HTMLDivElement>;
   introductionRef?: Ref<HTMLDivElement>;
+  /** Temporarily hide introductions without consuming their persisted state. */
+  showWelcomes?: boolean;
 }) {
   const { definition, invitation, welcome, welcomes, loading, enabled, checking, error } = companion;
   const [introductionId, setIntroductionId] = useState<string | null>(null);
@@ -60,7 +62,7 @@ export function TeacherCompanion({ companion, open, onOpen, onToggle, bubbleRef,
         <RefreshCw className={`h-3.5 w-3.5 shrink-0 ${companion.refreshing ? 'animate-spin motion-reduce:animate-none' : ''}`} aria-hidden="true" />
       </button>
       <span className="sr-only" role="status" aria-live="polite">{refreshMessage}</span>
-      {!invitation && welcomes.length > 0 && <div ref={bubbleRef} className="teacher-welcome-presence" data-testid="teacher-welcomes" aria-label="认识这里的老师">
+      {showWelcomes && !invitation && welcomes.length > 0 && <div ref={bubbleRef} className="teacher-welcome-presence" data-testid="teacher-welcomes" aria-label="认识这里的老师">
         <div className="teacher-welcome-list">
           {welcomes.map((item, index) => <article key={item.agentId} className="teacher-welcome-card" data-agent-id={item.agentId}
             data-tone={item.tone} style={{ '--welcome-delay': `${Math.min(index, 4) * 180}ms` } as CSSProperties}>
@@ -80,7 +82,7 @@ export function TeacherCompanion({ companion, open, onOpen, onToggle, bubbleRef,
           </article>)}
         </div>
       </div>}
-      {(invitation || welcome) && <div ref={bubbleRef} className="teacher-companion-presence" data-testid="teacher-presence">
+      {(invitation || (showWelcomes && welcome)) && <div ref={bubbleRef} className="teacher-companion-presence" data-testid="teacher-presence">
         <div className="teacher-companion-bubble" data-testid="teacher-invitation" data-bubble-kind={invitation ? 'check-in' : 'welcome'}>
           <div className="teacher-companion-bubble-heading">
             <div className="teacher-companion-invitation-label">{name}</div>