NES: Skip next cursor prediction when edit window covers entire file

[Copilot]

NES was making unnecessary nextCursorPosition API calls when the edit window already spans the entire document. Any predicted cursor line would fall within the edit window and be rejected with withinEditWindow error anyway.

Changes

• xtabProvider.ts: Early-out in doGetNextEditsWithCursorJump when editWindowLinesRange.containsRange(entireFileRange)
• Telemetry tracking via editWindowCoversWholeFile error type

const entireFileRange = OffsetRange.ofLength(promptPieces.currentDocument.lines.length);
if (promptPieces.editWindowLinesRange.containsRange(entireFileRange)) {
    telemetryBuilder.setNextCursorLineError('editWindowCoversWholeFile');
    return noSuggestions;
}

This commonly triggers for new/small files where the default edit window naturally covers the full document.

Original prompt

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This section details on the original issue you should resolve

<issue_title>NES: don't trigger next cursor line prediction when edit window is already the whole file</issue_title>
<issue_description></issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes NES: don't trigger next cursor line prediction when edit window is already the whole file vscode#271654

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