refactor: reduce ignored type errors in AST conversion

[3w36zj6]

No description provided.

[Copilot]

Pull Request Overview

This PR refactors the AST conversion module to reduce ignored TypeScript errors by improving type safety and replacing // @ts-expect-error comments with proper type handling. The changes introduce type guards, utility functions, and better-typed interfaces to handle the gradual transformation from Typst AST to textlint AST without suppressing type errors.

Key changes include:

• Added comprehensive type imports and type guards for AST node validation
• Introduced utility functions for safe property access and type checking
• Replaced property deletion using delete with Reflect.deleteProperty() for type safety

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[Copilot]

Creating a new RegExp object on every call is inefficient. Consider using RegExp.prototype.test directly or caching compiled regex patterns if they're reused frequently.

Suggested change

	const isTypstType = (type: string, pattern: string): boolean => {
	return new RegExp(pattern).test(type);
	const isTypstType = (type: string, pattern: RegExp): boolean => {
	return pattern.test(type);

[Copilot]

Double type assertion (as Content[] as TxtListItemNode[]) is a code smell that suggests type safety issues. Consider refining the types to avoid the need for this double assertion.