fix: force fresh API fetch on readdir to surface new remote files

[amlucas0xff]

Problem

Files added remotely (e.g. from an iOS device) never appear in a mounted iCloud Drive directory until the FUSE service is restarted.

Root Cause

pyicloud's DriveNode.get_children() maintains two layers of in-memory cache:

1. self.data["items"] — raw API response, populated on first fetch
2. self._children — parsed DriveNode objects built from data["items"]

get_children() only calls the API when "items" is absent from self.data. Once populated, both caches are never cleared, so the directory listing becomes permanently stale for the lifetime of the process.

Resetting only self._children is insufficient — it rebuilds children from the same stale data["items"] without making a new API call.

Fix

In readdir(), evict both cache layers before listing:

dh.data.pop("items", None)
dh._children = None

This forces get_children() to re-fetch directory contents from the iCloud API on every readdir call, so new files added remotely appear immediately on the next directory access without requiring a service restart.

Trade-off

Every directory listing now makes an API call. For typical interactive use (browsing, ls) this is acceptable. For high-frequency automated access, a TTL-based invalidation strategy would be preferable.