fix(ui): smooth mouse-wheel review scrolling

[benvinegar]

Summary

• replace the fixed multi-row mouse wheel jump with cadence-based OpenTUI acceleration
• keep single wheel ticks precise on small diffs while allowing sustained wheel gestures to speed up
• document the scrolling improvement in CHANGELOG.md

Testing

• bun run typecheck
• bun test src/ui/AppHost.interactions.test.tsx -t "mouse wheel scrolling updates the active file and hunk to the viewport center|shift plus mouse wheel scrolls code horizontally|shift plus mouse wheel does not move the vertical review position"
• bun test test/pty/ui-integration.test.ts -t "mouse wheel scrolling moves the review pane|the first mouse-wheel step still advances content under the always-pinned file header above a collapsed gap|one mouse-wheel step down then up restores the collapsed-gap view beneath the pinned file header"

This PR description was generated by Pi using OpenAI o3

[greptile-apps]

Greptile Summary

Replaces the previous fixed multi-row mouse-wheel jump with an OpenTUI MacOSScrollAccel-based approach that keeps single ticks precise while allowing sustained gestures to ramp up to 3× speed. The instance is correctly stabilized with useMemo([]) and the existing keyboard scrollStep=1 and shift+wheel horizontal scroll paths are unaffected.

Confidence Score: 5/5

Safe to merge — minimal, well-scoped change with no correctness issues

All three changed files are clean: the new factory is a single-responsibility wrapper, DiffPane correctly gates the instance behind useMemo, and the CHANGELOG entry lands in the right section. No P0/P1 findings.

No files require special attention

Important Files Changed

Filename	Overview
src/ui/lib/scrollAcceleration.ts	New file encapsulating MacOSScrollAccel instance creation with A=0.4, tau=4, maxMultiplier=3 — clean, single-responsibility factory function
src/ui/components/panes/DiffPane.tsx	Adds scrollAcceleration prop to the scrollbox via a useMemo-stabilized instance; keyboard step size (scrollStep=1) is unchanged and the existing shift+wheel horizontal scroll logic is unaffected
CHANGELOG.md	Entry correctly added to the [Unreleased] Fixed section

Sequence Diagram

sequenceDiagram
    participant User as User (wheel gesture)
    participant OT as OpenTUI ScrollBox
    participant MA as MacOSScrollAccel
    participant VP as DiffPane Viewport

    User->>OT: mouse wheel tick
    OT->>MA: computeMultiplier(timeSinceLastTick)
    MA-->>OT: multiplier (1.0 → up to 3.0)
    OT->>VP: scrollBy(delta × multiplier)
    VP-->>User: updated view

    Note over MA: A=0.4, tau=4, maxMultiplier=3<br/>First tick ≈ 1×, sustained burst → 3×

    User->>OT: shift + mouse wheel tick
    OT->>OT: onMouseScroll fires first
    OT->>VP: onScrollCodeHorizontally(±1)
    OT->>OT: queueMicrotask restores scrollTop/Left

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