fix(highlight): use the oniguruma engine so Go struct literals cannot freeze the page

[asnunes]

What

A review froze the browser tab completely: nothing clickable, and eventually Chrome reported the page as unresponsive.

Why

Shiki's JavaScript regex engine backtracks forever on one Go construct, an anonymous struct type whose literal follows }{ with nested braces and commas:

require.NoError(t, json.NewEncoder(w).Encode(struct {
	Items []contracts.Fact `json:"items"`
}{Items: []contracts.Fact{{Candidate: contracts.Candidate{Reference: reference, ChatID: "conversation", BusinessObjectID: "appointment", SourceFlow: "reminder"}, Eligible: true, Revision: "rev"}}}))

Highlighting runs synchronously during render, and a running regex cannot be interrupted, so the page locked up as soon as the window holding this code came within range of the viewport. The same file tokenizes in ~50 ms with the Oniguruma (WASM) engine, so the grammar is fine and the defect is in the JavaScript translation.

Change

• highlighter.ts uses createOnigurumaEngine(import("shiki/wasm")). The WASM (~230 KB gzipped) is a separate chunk fetched with the first grammar.
• Regression test with the real snippet. It hangs on the old engine and passes in milliseconds on the new one.

Notes

App.test.tsx > light and dark > puts the choice on the root element fails on main as well. It is unrelated to this change.

🤖 Generated with Claude Code

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