Persist robot state across page refreshes via localStorage

[Copilot]

Robot configuration, position, and block layout were lost on every page refresh. This adds full localStorage persistence to home.html.

What's saved

• Robot parts, position, angle, color, held block
• Motor power and turn speed settings
• All block positions, shapes, and colors

Implementation

saveState() — serializes state to localStorage under robotics_playground_state.

loadState() — called once before the game loop starts; restores all state and syncs UI elements (sliders, color picker, parts list, camera feed visibility, lidar panel).

Save triggers:

• Immediately on discrete actions: addPart, removePart, updatePower, updateTurn, updateColor, handlePickDrop
• Periodically (≤1s interval) inside loop() to capture position/angle during movement

Reset — resetAll() calls localStorage.removeItem(STORAGE_KEY) so a reset stays reset after refresh.

Restored x/y are clamped to current canvas bounds to handle viewport size changes between sessions. All localStorage calls are wrapped in try/catch to gracefully handle unavailability (e.g. private browsing, storage quota).

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