Fix inverted condition for module references in document highlights

The condition checking whether to return early for module references was inverted.
The TypeScript implementation returns early when the symbol is NOT transient,
but the Go code was returning early only when it IS transient.

This caused module symbols (whose declarations are SourceFiles with no parent)
to be passed to getReferencedSymbolsForSymbol, which then called
skipPastExportOrImportSpecifierOrUnion. That function would panic when
encountering a declaration without a parent for a non-transient symbol.

The fix aligns the Go implementation with the TypeScript source by checking
for `== 0` instead of `!= 0` on the transient flag.

Co-authored-by: jakebailey <[email protected]>

Author: Copilot

internal/ls/findallreferences.go

@@ -673,7 +673,7 @@ func (l *LanguageService) getReferencedSymbolsForNode(ctx context.Context, posit
 	}
 
 	moduleReferences := l.getReferencedSymbolsForModuleIfDeclaredBySourceFile(ctx, symbol, program, sourceFiles, checker, options, sourceFilesSet) // !!! cancellationToken
-	if moduleReferences != nil && symbol.Flags&ast.SymbolFlagsTransient != 0 {
+	if moduleReferences != nil && symbol.Flags&ast.SymbolFlagsTransient == 0 {
 		return moduleReferences
 	}
 

testdata/baselines/reference/fourslash/documentHighlights/documentHighlightImportPath.baseline.jsonc

@@ -0,0 +1,3 @@
+// === documentHighlights ===
+// === /b.ts ===
+// import { foo } from "/*HIGHLIGHTS*/my-module";