/**
 * ============================================================================
 * Welcome to DSA CheatSheet (dsacheatsheet.com)
 * A quick-revision IDE for senior engineers preparing for technical interviews
 * ============================================================================
 *
 * SHORTCUTS (remap any of them: Settings > Keymap, or press ? anytime)
 *   [Double Shift] or [Cmd/Ctrl+K] -> Search Everywhere (problems, patterns, tags)
 *   [Alt+Enter] (Option+Enter)     -> Ask AI about the selected text (deep dive & replace)
 *   [Cmd/Ctrl+Enter]               -> Run scratchpad (in-browser Python / JavaScript)
 *   [Alt+1]                        -> Toggle the project tree
 *   [Space], then [1] [2] [3]      -> Revise mode: reveal, then rate Forgot / Shaky / Solid
 *
 * HOW IT WORKS
 *   1. 4-Box Invariant method:
 *      Every problem has (1) the core trick, (2) exact TC/SC, (3) minimal code,
 *      (4) failure modes & follow-ups. Every snippet is test-verified.
 *
 *   2. Revise, don't re-read:
 *      Revise mode hides the answer until you recall it. Your ratings schedule
 *      the next review. See "Due today" in the status bar.
 *
 *   3. Local-first, then cloud:
 *      Notes and progress save in your browser instantly, no account needed.
 *      Sign in with Google or Apple to sync across devices and collaborate.
 *
 *   4. Upstream updates without losing your notes:
 *      When an official problem changes, click [Compare & Merge] to take the
 *      new parts and keep yours.
 *
 *   5. AI on any selection:
 *      Highlight text or code, ask a question, and replace or insert the answer
 *      (10 queries per day when signed in; chats are never stored on our servers).
 */