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/codexAppServerClient.test.ts

@@ -62,26 +62,6 @@ describe('CodexAppServerClient process cwd', () => {
         spawnMock.mockReset();
     });
 
-    it('uses null for legacy usage reads and opts in only when Reserve is supported', async () => {
-        const child = fakeChild();
-        child.stdin.write = vi.fn((_data: unknown, callback?: (error?: Error | null) => void) => {
-            callback?.();
-            return true;
-        });
-        spawnMock.mockReturnValue(child);
-        const client = new CodexAppServerClient({ cwd: '/neutral-home' });
-        await client.connect();
-        for (const supported of [false, true]) {
-            const pending = client.readAccountRateLimits(supported);
-            const request = JSON.parse(child.stdin.write.mock.lastCall![0] as string);
-            expect(request.method).toBe('account/rateLimits/read');
-            expect(request.params).toEqual(supported ? { supportsLunaReserve: true } : null);
-            child.stdout.emit('data', Buffer.from(JSON.stringify({ id: request.id, result: { rateLimits: {} } }) + '\n'));
-            await expect(pending).resolves.toEqual({ rateLimits: {} });
-        }
-        await client.disconnect();
-    });
-
     it('passes an explicit neutral cwd to the app-server process', async () => {
         spawnMock.mockReturnValue(fakeChild());
         const client = new CodexAppServerClient({ cwd: '/neutral-home' });