🧹 Refactor scroll implementation into OS-specific helper functions

[undivisible]

🎯 What: The scroll function in src/lib.rs was 81 lines long due to heavy #cfg conditionals mixing macOS, Windows, and Linux logic into a single method body.
💡 Why: Splitting this logic into discrete windows_scroll and mac_scroll helper functions drastically simplifies the main scroll dispatch block, enhancing readability and isolating OS-specific code paths, which improves maintainability.
✅ Verification: Validated that functionality is logically equivalent, confirmed no new issues were introduced via cargo check, cargo fmt, cargo clippy, and verified successfully against the local unit test suite cargo test --lib.
✨ Result: The scroll function is now clean, readable, and properly delegates to its newly extracted OS-specific counterparts.

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PR created automatically by Jules for task 6718624537651276967 started by @undivisible

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Note

Low Risk
Mechanical move of platform scroll code with no intended behavior change; Linux path untouched.

Overview
Refactors native scroll input so Windows and macOS logic live in dedicated helpers instead of a long inline scroll method.

windows_scroll and mac_scroll hold the existing SendInput / Core Graphics scroll-wheel behavior unchanged. NativeRuntime::scroll now only dispatches to Linux (native_scroll), windows_scroll, or mac_scroll behind the same #[cfg] gates as before.

^{Reviewed by Cursor Bugbot for commit 70ddf73. Configure here.}

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