fix: ConstTag AST tweak (#11196)

VariableDeclaration should start at `const`, not at `@const`
As a side-effect, this will create less diff noise for language tools tests

packages/svelte/src/compiler/phases/1-parse/state/tag.js

@@ -565,7 +565,7 @@ function special(parser) {
 				type: 'VariableDeclaration',
 				kind: 'const',
 				declarations: [{ type: 'VariableDeclarator', id, init }],
-				start: start + 1,
+				start: start + 2, // start at const, not at @const
 				end: parser.index - 1
 			}
 		});