feat: add parent-only disclaimer and report link to session cost

The Visible Context panel's Session Cost only reflects the parent
session. Add "(parent only · view full cost)" label that links to
the Session Report where parent + subagent costs are shown.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/renderer/components/chat/ChatHistory.tsx

@@ -64,6 +64,7 @@ export const ChatHistory = ({ tabId }: ChatHistoryProps): JSX.Element => {
     syncSearchMatchesWithRendered,
     selectSearchMatch,
     setTabVisibleAIGroup,
+    openSessionReport,
   } = useStore(
     useShallow((s) => ({
       searchQuery: s.searchQuery,
@@ -76,6 +77,7 @@ export const ChatHistory = ({ tabId }: ChatHistoryProps): JSX.Element => {
       syncSearchMatchesWithRendered: s.syncSearchMatchesWithRendered,
       selectSearchMatch: s.selectSearchMatch,
       setTabVisibleAIGroup: s.setTabVisibleAIGroup,
+      openSessionReport: s.openSessionReport,
     }))
   );
 
@@ -872,6 +874,7 @@ export const ChatHistory = ({ tabId }: ChatHistoryProps): JSX.Element => {
               onNavigateToUserGroup={handleNavigateToUserGroup}
               totalSessionTokens={lastAiGroupTotalTokens}
               sessionMetrics={sessionDetail?.metrics}
+              onViewReport={effectiveTabId ? () => openSessionReport(effectiveTabId) : undefined}
               phaseInfo={sessionPhaseInfo ?? undefined}
               selectedPhase={selectedContextPhase}
               onPhaseChange={setSelectedContextPhase}

src/renderer/components/chat/SessionContextPanel/components/SessionContextHeader.tsx

@@ -29,6 +29,7 @@ interface SessionContextHeaderProps {
   totalSessionTokens?: number;
   sessionMetrics?: SessionMetrics;
   onClose?: () => void;
+  onViewReport?: () => void;
   phaseInfo?: ContextPhaseInfo;
   selectedPhase: number | null;
   onPhaseChange: (phase: number | null) => void;
@@ -42,6 +43,7 @@ export const SessionContextHeader = ({
   totalSessionTokens,
   sessionMetrics,
   onClose,
+  onViewReport,
   phaseInfo,
   selectedPhase,
   onPhaseChange,
@@ -132,6 +134,22 @@ export const SessionContextHeader = ({
               <span className="font-medium tabular-nums" style={{ color: COLOR_TEXT_SECONDARY }}>
                 {formatCostUsd(sessionMetrics.costUsd)}
               </span>
+              <span style={{ color: COLOR_TEXT_MUTED }}> (parent only</span>
+              {onViewReport ? (
+                <span>
+                  <span style={{ color: COLOR_TEXT_MUTED }}> · </span>
+                  <button
+                    onClick={onViewReport}
+                    className="underline"
+                    style={{ color: COLOR_TEXT_SECONDARY }}
+                  >
+                    view full cost
+                  </button>
+                  <span style={{ color: COLOR_TEXT_MUTED }}>)</span>
+                </span>
+              ) : (
+                <span style={{ color: COLOR_TEXT_MUTED }}>)</span>
+              )}
             </div>
           )}
         </div>

src/renderer/components/chat/SessionContextPanel/index.tsx

@@ -49,6 +49,7 @@ export const SessionContextPanel = ({
   onNavigateToUserGroup,
   totalSessionTokens,
   sessionMetrics,
+  onViewReport,
   phaseInfo,
   selectedPhase,
   onPhaseChange,
@@ -193,6 +194,7 @@ export const SessionContextPanel = ({
         totalSessionTokens={totalSessionTokens}
         sessionMetrics={sessionMetrics}
         onClose={onClose}
+        onViewReport={onViewReport}
         phaseInfo={phaseInfo}
         selectedPhase={selectedPhase}
         onPhaseChange={onPhaseChange}

src/renderer/components/chat/SessionContextPanel/types.ts

@@ -27,6 +27,8 @@ export interface SessionContextPanelProps {
   totalSessionTokens?: number;
   /** Full session metrics (input, output, cache tokens, cost) */
   sessionMetrics?: SessionMetrics;
+  /** Open the Session Report to see full cost breakdown */
+  onViewReport?: () => void;
   /** Phase information for phase selector */
   phaseInfo?: ContextPhaseInfo;
   /** Currently selected phase (null = current/latest) */