fix: clear cockpit state on session switch and add loading placeholders

- Reset triageMeta, psaTicketId, steps, and completedSteps when
  activeChatId changes (prevents stale triage data from previous session
  showing while AI processes the new one)
- Split the activeChatId and activeActions reset effects so triage
  only resets on session switch, not on every new action set
- Add loading placeholders to cockpit work zone: spinner + "analyzing"
  text in steps panel, "questions will appear here" in right panel
- Add centered "Starting session..." loader to FlowPilot page when
  loading with no messages yet (prefill creation period)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/pages/CockpitPage.tsx

@@ -87,11 +87,23 @@ export default function CockpitPage() {
     prevMessageCountRef.current = session.messages.length
   }, [session.messages.length, showOnboarding])
 
-  // Reset local step UI when switching cases or when a new action set arrives.
+  // Reset all cockpit-local state when switching cases.
+  // Triage data gets repopulated via onSessionLoadedRef after the async fetch.
   useEffect(() => {
     setActiveStepIndex(0)
     setCompletedSteps(new Set())
-  }, [session.activeChatId, session.activeActions])
+    setTriageMeta({
+      client_name: null, asset_name: null, issue_category: null,
+      triage_hypothesis: null, evidence_items: [],
+    })
+    setPsaTicketId(null)
+  }, [session.activeChatId])
+
+  // Reset step UI when a new action set arrives from AI.
+  useEffect(() => {
+    setActiveStepIndex(0)
+    setCompletedSteps(new Set())
+  }, [session.activeActions])
 
   // ── Triage handlers ──
 
@@ -306,28 +318,44 @@ export default function CockpitPage() {
               <div className="flex min-h-0 overflow-hidden" style={{ height: `${workZonePct}%` }}>
                 {/* Left: Steps panel */}
                 <div className="flex-[55] min-w-0 p-3 overflow-y-auto border-r border-default">
-                  <StepsPanel
-                    actions={session.activeActions}
-                    activeIndex={activeStepIndex}
-                    completedSteps={completedSteps}
-                    onStepComplete={handleStepComplete}
-                    onStepSelect={handleStepSelect}
-                  />
+                  {session.loading && session.activeActions.length === 0 ? (
+                    <div className="flex flex-col items-center justify-center h-full text-center gap-2">
+                      <Loader2 size={20} className="animate-spin text-accent" />
+                      <p className="text-xs text-muted-foreground">FlowPilot is analyzing the issue...</p>
+                    </div>
+                  ) : (
+                    <StepsPanel
+                      actions={session.activeActions}
+                      activeIndex={activeStepIndex}
+                      completedSteps={completedSteps}
+                      onStepComplete={handleStepComplete}
+                      onStepSelect={handleStepSelect}
+                    />
+                  )}
                 </div>
                 {/* Right: FlowPilot Asks + What We Know */}
                 <div className="flex-[45] min-w-0 p-3 overflow-y-auto flex flex-col gap-3">
-                  <FlowPilotAsks
-                    questions={session.activeQuestions}
-                    onAnswer={(answer) => {
-                      void session.sendMessage(answer, { clearComposer: false })
-                    }}
-                    loading={session.loading}
-                  />
-                  <WhatWeKnow
-                    items={triageMeta.evidence_items}
-                    onAdd={handleEvidenceAdd}
-                    onEdit={handleEvidenceEdit}
-                  />
+                  {session.loading && session.activeQuestions.length === 0 && triageMeta.evidence_items.length === 0 ? (
+                    <div className="flex flex-col items-center justify-center h-full text-center gap-2">
+                      <Sparkles size={18} className="text-muted" />
+                      <p className="text-xs text-muted-foreground">Questions and evidence will appear here</p>
+                    </div>
+                  ) : (
+                    <>
+                      <FlowPilotAsks
+                        questions={session.activeQuestions}
+                        onAnswer={(answer) => {
+                          void session.sendMessage(answer, { clearComposer: false })
+                        }}
+                        loading={session.loading}
+                      />
+                      <WhatWeKnow
+                        items={triageMeta.evidence_items}
+                        onAdd={handleEvidenceAdd}
+                        onEdit={handleEvidenceEdit}
+                      />
+                    </>
+                  )}
                 </div>
               </div>
 

frontend/src/pages/FlowPilotPage.tsx

@@ -149,6 +149,12 @@ export default function FlowPilotPage() {
                         </p>
                       </div>
                     )}
+                    {session.messages.length === 0 && session.loading && (
+                      <div className="flex flex-col items-center justify-center h-full text-center gap-3">
+                        <Loader2 size={24} className="animate-spin text-primary" />
+                        <p className="text-sm text-muted-foreground">Starting session...</p>
+                      </div>
+                    )}
                     {session.messages.map((msg, i) => (
                       <ChatMessage
                         key={i}