[find-ui] Allow users to retrieve untruncated, paste-ready samples with --id

## Summary

`winapp find-ui --id ` does not always return a complete, paste-ready/buildable sample. Some results contain an explicit `` marker, including `toolkit-tabbedcommandbar-1`, `gallery-gridview-2`, and `toolkit-gridsplitter-1`.

## Reproduction

```powershell
winapp find-ui --id toolkit-tabbedcommandbar-1
```

The returned XAML ends early and contains:

```xml

```

## Question / proposed direction

Do we need an option that lets users request the full, untruncated snippet? For example, `--full`, `--no-truncate`, or another explicit mode could preserve concise default output while allowing users and agents to retrieve complete code.

Whichever behavior we choose, the command should make clear whether the result is intended to be directly buildable. If full source cannot be returned, it should provide a source URL or another deterministic way to retrieve it.

## Expected behavior

Users and agents should have a documented way to retrieve a complete sample, including required XAML/C# and prerequisite notes, without silently receiving incomplete code.