Set scrolling_history to 100,000

[gene1wood]

Relates to #684

2026-05-29_11-36-02.mp4

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[gene1wood]

@jackpot51

You wrote in #684 (comment)

To follow up on what @maria-komarova said, I think we are okay to hard-code the maximum scrollback alacritty_terminal allows, 100,000 lines, until it can be made larger.

This PR does that.