fix: prevent cursor overflow with long input

[echobt]

Description

This PR addresses an issue where extremely long input strings in the search TUI could cause an integer overflow when calculating the cursor position. The cursor position calculation now clamps the input length to the visible input area width, ensuring it fits within u16 and remains within the bounds of the terminal area.

Changes

• Updated search_tui.rs to calculate max_input_width based on area width minus borders.
• Clamped input_len to the minimum of the actual input length and max_input_width, casting strictly to u16 only after clamping.
• Updated set_cursor_position to use the safe, clamped value.

Verification

• Verified manually with a reproduction test case that simulated the overflow condition.
• The cursor is now correctly positioned at the end of the visible input area even when the input string exceeds u16::MAX.