Fix InternalScreen bounds checks

[dyxushuai]

Problem

InternalScreen bounds checks used strict < comparisons. This lets width == col or height == row pass, which can alias the next row (for width == col) or hit the bounds assert on the last row.

Fix

• Use self.width <= col / self.height <= row checks for read/write.
• Add a test that covers out-of-bounds access at col == width.

Tests

• zig test src/InternalScreen.zig

[Copilot]

Pull request overview

This PR fixes incorrect bounds checking in InternalScreen that allowed out-of-bounds column and row access to pass through, potentially causing memory aliasing or assertion failures.

• Changed bounds check conditions from self.width < col to col >= self.width (and equivalent for rows) to correctly reject boundary values
• Added a test case to verify that writes at col == width are properly rejected and don't corrupt adjacent cells

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[rockorager]

Thanks!