Add JSDoc documentation to App.jsx

[Copilot]

Added comprehensive JSDoc documentation to the Superhero Comparison App component.

Changes

• File-level: @fileoverview describing component purpose and key features
• Component and functions: JSDoc blocks with @param, @returns, and @component annotations for:
  • Main App component
  • Event handlers (handleHeroSelection, handleCompare, handleBackToTable)
  • Utility functions (isHeroSelected, calculateWinner)
  • Render functions (renderComparison, renderTable)
• Inline comments: State variable purposes, conditional logic branches, and UI section markers

Example of function documentation added:

/**
 * Calculate which hero wins based on their powerstats.
 * Compares all six stats: intelligence, strength, speed, durability, power, combat.
 * The hero with more winning stats is the winner.
 * 
 * @param {Object} hero1 - First superhero to compare
 * @param {Object} hero2 - Second superhero to compare
 * @returns {Object} Result object containing:
 *   - winner: The winning hero object, or null if there's a tie
 *   - score: String representation of the score (e.g., "4-2")
 */
const calculateWinner = (hero1, hero2) => {
  // ...
};

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add documentation to frontend/src/App.jsx</issue_title>
<issue_description>Add documentation to frontend/src/App.jsx:

• Overall file doc
• Function docs
• Inline docs</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add documentation to frontend/src/App.jsx #4

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