Add Svelte syntax highlighting support for code blocks

Summary

Code blocks with the svelte language tag are not syntax highlighted in Claude Code's terminal output. Since Svelte is a popular frontend framework, it would be great to have proper syntax highlighting support.

Current Behavior

When Claude outputs a fenced code block with `svelte , it renders as plain uncolored text.

Expected Behavior

Svelte code blocks should render with syntax highlighting, similar to how HTML, TypeScript, and other languages are highlighted. Svelte is a superset of HTML, so at minimum HTML/CSS/JS portions should highlight, ideally with Svelte-specific syntax ({#if}, {#each}, $state, $derived, $effect, etc.) supported as well.

Additional Context

Users working in SvelteKit projects frequently receive Svelte code output from Claude, and the lack of highlighting makes it harder to read in the terminal.