Add XML documentation for Android.Health.Connect

The `Android.Health.Connect` namespace contains **799** `To be added` placeholders in source XML documentation (excluding `docs\xml\index.xml`).

Example command:

```powershell
rg -n -i --glob 'Android.Health.Connect/**' --glob 'ns-Android.Health.Connect.xml' 'to be added' docs\xml
```

## Update log

- 2026-09-10: Refreshed the placeholder scan from **781** to **799** (increased by **18**). Related documentation PRs: [#644](https://github.com/dotnet/android-api-docs/pull/644).

Start by running the provided rg scan under docs\xml for Android.Health.Connect and inspect the matching namespace and source XML documentation files. Work through the 799 “To be added” entries; done means the namespace’s placeholders are replaced with documentation and the scan no longer reports them, excluding docs\xml\index.xml.

Vom Indexierungsmodell aus dem Issue-Text verfasst.