Address scattered TODO/FIXME comments throughout codebase

Summary

Multiple TODO and FIXME comments are dispersed across the repository, particularly in:

• Dependency/prism components (e.g., prism-wiki.js, prism-rust.js, prism-pascal.js, prism-perl.js, prism-haml.js, prism-smarty.js)
• MacDown Resources/Prism components (same languages)
• peg-markdown-highlight/HGMarkdownHighlighter.m (todo: throw exception if targetTextView is nil?)
• Dependency/YAML-framework/YAMLSerialization.m (several TODO/FIXME comments)

These comments indicate incomplete implementations, missing error handling, or planned enhancements that should be tracked and resolved.

Suggested Actions

1. Categorize each TODO/FIXME by severity and component.
2. Create sub-tasks or individual issues for each pending item.
3. Assign owners and set target milestones for completion.
4. Remove or document the TODOs once the associated work is done.

Example Items

• in several prism components – ensure multi-line support is implemented.
• – evaluate and implement if needed.
• – verify against YAML spec and implement validation.
• – add nil-check and appropriate exception handling.

This issue tracks the overall effort to clean up the TODO/FIXME backlog across the codebase.

Start with a repository-wide search for TODO and FIXME comments, focusing on the listed Prism files, peg-markdown-highlight/HGMarkdownHighlighter.m, and Dependency/YAML-framework/YAMLSerialization.m. Categorize each item by component and severity, then track actionable work as sub-issues; done means pending items are resolved or documented with ownership and milestones.