Error recovery: no retry path once an observable cache entry errors

从 preloadObservable 和全局 preloadedObservables 缓存开始，然后通过 hook 的非 Suspense 状态路径跟踪 SuspenseSubject 的错误和重置行为。完成标准是：约定的重试或重置路径能够让出错条目使用相同的 observableId 恢复，而不需要不同的 ID 或 remount 变通方案。

Problem

Once a reactfire hook enters status: 'error', there is no way to recover without remounting with a different observableId.

The errored SuspenseSubject stays in the global preloadedObservables cache under its observableId. On error, the 30-second reset timer is cancelled (it becomes a no-op timeout), and the observable does not re-subscribe. A component that remounts with the same observableId rejoins the same errored subject and immediately receives status: 'error' again.

This became user-visible in v4.3.0, which made status: 'error' reachable in non-suspense mode (previously errors always threw, so the stuck state was hidden). Users building status === 'error' UI now have no way to trigger a retry.

Current workaround

Change the observableId passed to the hook. This causes preloadObservable to create a fresh SuspenseSubject and re-subscribe to the source. Not a real API — just an escape hatch.

What a fix might look like

• An explicit retry() / reset() function returned from the hook, or
• A retryOnError option that re-subscribes automatically after a delay, or
• Cache eviction on error after the reset timeout (restoring the pre-v4.3 behavior for the cache entry, not for error surfacing)

The right shape is an open question. Filing to track the gap.

Closes none. Related to #735.