Add XML documentation for Android.Media.TV

The `Android.Media.TV` namespace contains **1,004** `To be added` placeholders in source XML documentation (excluding `docs\xml\index.xml`).

Example command:

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

## Update log

- 2026-09-10: Refreshed the placeholder scan from **1,464** to **1,004** (reduced by **460**). Related documentation PRs: [#644](https://github.com/dotnet/android-api-docs/pull/644), [#663](https://github.com/dotnet/android-api-docs/pull/663).

Run the provided rg command against docs\xml to enumerate the 1,004 placeholders under Android.Media.TV, then inspect the matching namespace and API XML files for the surrounding declarations. Replace each placeholder with accurate Android.Media.TV API documentation and rerun the scan until no matching placeholders remain.

Scritto dal modello di indicizzazione a partire dal testo della issue.