Synology: taildrive from Synology exposes internal @eaDir directories

### What is the issue?

Sharing a taildrive from a Synology device exposes all the internal `@eaDir` directories that are used by Synology for internal book keeping and filtered out when using Synology's own `SMB` implementation or file browser.

These files should probably not be surfaced through the taildrive?

### Steps to reproduce

1. Expose a Shared Folder from a Synology device (following [instructions](https://tailscale.com/docs/features/taildrive?tab=synology#sharing-and-accessing-folders-with-taildrive)).
- `tailscale drive share media /volume3/media`
3. Access the shared folder from a user with `rw` permissions.
4. Notice `@eaDir` directories (normally hidden).
5. Attempt to recursively add music to `vlc`
6. VLC gets very upset about some of the files (inside `@eaDir` folders).

### Are there any recent changes that introduced the issue?

Enabling Taildrive & sharing from the Synology device.

### OS

Synology

### OS version

DSM 7.4.1-90080

### Tailscale version

1.102.4-t3caf7d9e7-g084ee3b64

### Other software

Not using the Tailscale.com controlplane, but headscale.net version `0.29.3`.

Bug report identifier captured from the Synology device itself.

### Bug report

BUG-9616f5828cf901c1a32ee2bb66cb6c4e3be63384f947f6a16ec40f35bc4c34b6-20260912131748Z-e76c5e1c10069322

Start with the Taildrive Synology sharing path and the `tailscale drive share media /volume3/media` entry point, then reproduce the shared-folder access described in the issue. Done means `@eaDir` directories and their files are not surfaced through Taildrive, including during recursive music import in VLC.

Written by the indexing model from the issue text.