⚡ Bolt: Memoize SimulationGrid game cells to prevent re-renders on hover

[google-labs-jules]

💡 What: Extracted the individual game cell divs inside SimulationGrid.tsx into a memoized GameCellDisplay component. Defined handleMouseEnter and handleMouseLeave globally within SimulationGrid using useCallback to pass stable function references down to the child components.
🎯 Why: Previously, hovering over any game cell updated the hoveredGame state at the top-level SimulationGrid component. Because the game cells were rendered inline and lacked stable event handler references or memoization, this caused a full re-render of thousands of DOM elements on every single hover event (or mouse exit event), leading to a noticeable UI lag/bottleneck.
📊 Impact: Reduces React re-renders by ~99% during hover interactions within the grid. Rather than rendering 100+ (or 1000+) game cells per state change, React will only re-render the single SimulationGrid wrapper and the isolated Tooltip rendering the hoveredGame details.
🔬 Measurement: Open the React Profiler in developer tools, record an interaction while hovering rapidly across the grid. The commit should change the Profiler flamegraph from showing a massive wall of SimulationGrid -> div renders to nearly instant renders.

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PR created automatically by Jules for task 327040818803171881 started by @TytaniumDev

[google-labs-jules]

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[claude]

Code Review - Approved

No issues found. Checked for bugs, security issues, and CLAUDE.md compliance.

Changes reviewed

frontend/src/components/SimulationGrid.tsx

• The GameCellDisplay memoized component is correctly structured. Its props (game, cellSize, onMouseEnter, onMouseLeave) are all unaffected by hoveredGame state changes in the parent, so memo will correctly prevent unnecessary re-renders on hover.
• handleMouseEnter and handleMouseLeave are properly stabilized with useCallback (empty deps), ensuring stable references are passed to GameCellDisplay.
• The inline () => onMouseEnter(game) arrow function inside GameCellDisplay creates a new function reference on each render of that component, but since GameCellDisplay itself is memoized and won't re-render on hover state changes, this is not a performance problem.
• The optimization achieves the stated goal: hovering a single cell no longer triggers a full grid re-render.

Deleted files

• verify_simulation_grid.py and verification_simulation_grid.png are temporary verification artifacts that do not belong in the repository. Their removal is correct.