Character references for IVS doesn’t work#15821

### Describe the bug Character references defined in HTML[1] for ideographic variation sequences (IVS) defined in Unicode[2] doesn’t work. 1. https://html.spec.whatwg.org/multipage/syntax.html#character-references 2. https://www.unicode.org/reports/tr37/ ### Reproduction 1. Make a minimal project by `npx sv`. 2. Download a font file “Noto Serif JP” from Google Fonts (https://fonts.google.com/noto/specimen/Noto+Serif+JP) (the Google Fonts’ webpage uses the name “Noto Serif Japanese” but internally it seems to use the name “Noto Serif JP”). 3. Place the downloaded font file `NotoSerifJP-VariableFont_wght.ttf` to the `static` directory of the project. 4. Write the following to `src/routes/+page.svelte`: ```svelte <div class="font-noto-serif-jp"> 通&#xE0100;通&#xE0101; </div> <style> @font-face { font-family: "Noto Serif JP"; src: url("/NotoSerifJP-VariableFont_wght.ttf") format("truetype"); } .font-noto-serif-jp { font-family: "Noto Serif JP"; } </style> ``` 5. Check the following output: <img width="45" alt="Image" src="https://github.com/user-attachments/assets/76089750-9cca-494e-abb2-0cb74d27159b" /> The first character must has one point at the top‐left, and the second character must has two points at the top‐left. So they must be different. However, both have only one point, they are same. We can confirm naive HTML + CSS gives the desired result: <img width="44" alt="Image" src="https://github.com/user-attachments/assets/2c04f982-4d88-440a-9226-8681966ffbf0" /> ### Logs ```shell ``` ### System Info ```shell npx envinfo --system --npmPackages svelte,roolup,webpack --binaries --browsers System: OS: macOS 15.4.1 CPU: (8) arm64 Apple M3 Memory: 226.14 MB / 24.00 GB Shell: 4.0.1 - /opt/homebrew/bin/fish Binaries: Node: 23.11.0 - /opt/homebrew/bin/node npm: 10.9.2 - /opt/homebrew/bin/npm pnpm: 10.7.0 - ~/Library/pnpm/pnpm Browsers: Safari: 18.4 npmPackages: svelte: ^5.0.0 => 5.28.2 ``` ### Severity annoyance