fix(emmet): pass syntax hint to extractAbbreviation in expandEmmetAbbreviation

[yogeshwaran-c]

Upstream fix for #233969

Problem

When a language is mapped to HTML via emmet.includeLanguages (e.g. "erb": "html"), typing a class abbreviation like .foo and pressing Tab fails to expand it. The abbreviation extractor picks up an empty or incorrect range because it does not know whether to apply stylesheet or markup extraction rules.

Root Cause

expandEmmetAbbreviation calls helper.extractAbbreviation(...) without the syntax option, so the helper defaults to markup mode for all documents — including stylesheet languages — and vice versa. Compare with defaultCompletionProvider.ts which already passes the correct syntax value:

// defaultCompletionProvider.ts (correct)
helper.extractAbbreviation(doc, pos, { lookAhead: false, syntax: isStyleSheet(syntax) ? 'stylesheet' : 'markup' });

Fix

Add the same syntax option to the extractAbbreviation call inside expandEmmetAbbreviation:

// Before
const extractedResults = helper.extractAbbreviation(
    toLSTextDocument(editor.document), position, { lookAhead: false });

// After  
const extractedResults = helper.extractAbbreviation(
    toLSTextDocument(editor.document), position,
    { lookAhead: false, syntax: isStyleSheet(syntax) ? 'stylesheet' : 'markup' });

This is a one-line change that aligns expandEmmetAbbreviation with the existing behaviour in defaultCompletionProvider.ts.