revert(codex): remove Luna Reserve fallback (#1780)

Revert 8357da0a9d and its later shared-runtime integration.

Remove automatic model fallback, account usage polling, and the related UI, protocol fields, tests, and documentation without adding replacement quota handling.

Keep generic model pagination and method probing required by the current shared-session architecture. Cover idle sessions staying online without usage polling or agent-state churn.

cli/src/codex/shared/root.test.ts

@@ -31,7 +31,10 @@ vi.mock('../utils/buildHapiMcpBridge', () => ({ buildHapiMcpBridge: async () =>
 }) }));
 
 const cleanups: Array<() => Promise<void>> = [];
-afterEach(async () => { for (const cleanup of cleanups.splice(0)) await cleanup(); });
+afterEach(async () => {
+    try { for (const cleanup of cleanups.splice(0)) await cleanup(); }
+    finally { vi.useRealTimers(); }
+});
 
 async function fixture() {
     const directory = await mkdtemp('/tmp/hapi-shared-root-');
@@ -45,7 +48,7 @@ async function fixture() {
         updateAgentState: updateState, keepAlive() {},
         onUserMessage() {}, onCancelQueuedMessage() {}, onRetryQueuedMessage() {},
         onReconnect: (fn: (() => void) | null) => { reconnect = fn; },
-        rpcHandlerManager: { registerHandler() {} }, sendSessionEvent() {}, sendAgentMessage() {},
+        rpcHandlerManager: { registerHandler() {} }, sendSessionEvent() {}, sendAgentMessage() {}, emitSessionReady() {},
         sendSessionDeath() {}, async flush() {}, close() {}
     } as unknown as ApiSessionClient;
     const root = new SharedCodexRoot({ session, workingDirectory: directory } as SessionBootstrapResult, {
@@ -66,6 +69,21 @@ async function fixture() {
 }
 
 describe('shared steering availability', () => {
+    it('keeps idle sessions online without polling usage or publishing agent-state updates', async () => {
+        const f = await fixture();
+        const requests = vi.spyOn(f.root.client, 'request');
+        const heartbeat = vi.spyOn(f.root.session, 'keepAlive');
+        const updates = f.updateState.mock.calls.length;
+        vi.useFakeTimers();
+
+        await f.root.activate();
+        await vi.advanceTimersByTimeAsync(5 * 60_000);
+
+        expect(heartbeat).toHaveBeenCalled();
+        expect(requests).not.toHaveBeenCalled();
+        expect(f.updateState).toHaveBeenCalledTimes(updates);
+    });
+
     it('publishes root turn transitions, ignores child turns, and clears on shutdown', async () => {
         const f = await fixture();
         expect(f.state().steeringActive).toBe(false);