144Implement a browser IDE with syntax highlighting, files, tabs, and isolated code execution

Build the core of a CodeSandbox-style IDE: the parts behind the UI.

1. File system createFileSystem(): writeFile(path, content) (creating parent folders), readFile(path), mkdir(path), rename(from, to) (moving a folder moves everything inside), remove(path) (recursive), exists(path), list(dir) (entry names, folders first, then alphabetical), and files() (every file path). Paths are absolute (/src/app.js); throw an Error for missing paths.
2. Tabs createTabs(): open(path) (no duplicates; activates it), close(path) (activates the tab to the right, else the left), setDirty(path, dirty), closeOthers(path), reopenClosed() (the most recently closed), and state() returning { tabs: [{ path, dirty }], active }.
3. Syntax highlighting tokenize(code): an array of { type, value } with types keyword, string (single, double and template quotes), number, comment (line and block), identifier, punctuation and whitespace. Joining all values must give back the exact input.
4. Isolated execution runProject(fs, entry, { timeout = 1000 }): run the project's JavaScript in a fresh Web Worker with a CommonJS require that resolves relative paths between project files (require("./utils") → /src/utils.js), capturing console.log lines. Resolve { logs }, or { logs, error } if the code throws, or reject with an error named "TimeoutError" (terminating the worker) after timeout ms.