fix: strip comments from inline style values in linear time (#18553)

`to_style()` strips CSS comments from an inline `style` value with
`/\s*\/\*.*?\*\/\s*/g`. The leading `\s*` makes the match retry from
every position, so a long run of whitespace backtracks in O(n^2). When a
dynamic `style={value}` sits on an element that also has a `style:`
directive, that regex runs on `value`, so a large whitespace string can
stall rendering (server) or the main thread (client).

### Fix

Drop the surrounding `\s*` and match only the comment: `/\/\*.*?\*\//g` to prevent quadratic regex.
The surrounding whitespace was already removed by the `.trim()`

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>

.changeset/strip-style-comments.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: strip comments from inline `style` values in linear time

packages/svelte/src/internal/shared/attributes.js

@@ -142,8 +142,9 @@ export function to_style(value, styles) {
 		}
 
 		if (value) {
+			// strip comments; surrounding whitespace is handled by the trims below (which is much faster than doing it through regex)
 			value = String(value)
-				.replaceAll(/\s*\/\*.*?\*\/\s*/g, '')
+				.replaceAll(/\/\*.*?\*\//g, '')
 				.trim();
 
 			/** @type {boolean | '"' | "'"} */