Add virtual portfolio filesystem commands

[cursor]

Summary

• Adds a read-only /home/guest portfolio filesystem generated from existing site JSON data.
• Wires pwd, ls, cd, cat, and tree into the terminal runtime with path-aware prompts.
• Documents the filesystem command surface and adds focused unit coverage.

Issue

Title

Improve terminal emulation with a navigable portfolio filesystem

Problem

The terminal exposed shell-like commands such as pwd, ls, and cd, but they did not behave like a real filesystem: pwd was static, ls listed commands, and cd could not navigate portfolio content.

Proposed solution

Generate a read-only virtual filesystem from existing portfolio data and expose it through shell-style commands so visitors can explore projects, skills, experience, blog posts, contact info, and resume metadata from the terminal.

Acceptance criteria

• pwd reflects the current directory.
• ls [path] lists generated directories/files, while ls --commands keeps command discovery available.
• cd [path] supports relative paths, absolute paths, .., ., and ~.
• cat [file] prints generated file content and errors on missing paths/directories.
• tree [path] renders a directory tree.
• README and unit tests cover the new behavior.

Verification

• git push -u origin cursor/terminal-emulation-feature-9a02 ran the pre-push npm run check suite successfully: lint, format check, coverage tests, and build.