feat: let agents read supervisor story graphs

Expose saved decisions, timelines and source evidence through read-only Story Graph tools across Model, Harness and local/remote OpenCode and Continue. Supervisor enablement and runtime assignments govern discovery and calls; reads do not invoke models or modify stored evidence. Remote use requires matching Desktop and Agent changes.

Make Continue discussion show the complete editable message with a separated destination and shared action layout. Sending uses the visible draft without reattaching removed context.

Validation: existing focused MCP, runtime, controlled Linux Host, discussion component and Electron layout checks plus typechecks; staged diff check passed. Cross-scope fact reuse, historical reconstruction and full package acceptance remain deferred.

Release note: Agents can consult saved supervisor decisions and their sources when continuing work. Continue discussion now lets you review and edit the complete message before sending.

tests/support/supervisor-layout-regression.tsx

@@ -244,10 +244,12 @@ createRoot(document.getElementById('root')!).render(
           </a>
         ))}
       </div>
-      {params.has('sidebar') ? <div className="assistant-sidebar__section task-center">
+      {params.has('sidebar') ? <div className="assistant-sidebar__section task-center" style={{ overflowY: 'auto', minHeight: 0 }}>
         <SupervisionCard
           target={{ type: 'conversation', conversationId: 'simulated-conversation-uuid' }}
           conversationTitle={'模拟会话：核对项目交付清单与阶段回顾'.repeat(3)}
+          activeConversationId="simulated-conversation-uuid"
+          onContinueSupervision={async () => { throw new Error('Preview fixture must not send a message') }}
           pinned
           onTogglePinned={() => {}}
         />