fix(web): keep diff file lists scrollable past expanded files

[dominic-r]

In a pull request's Code tab, expanding a file left the file rows after it clipped at the bottom of the scroll area — with a file open mid-list you could scroll until the next file's row peeked in cut off, and the rows past it were unreachable.

Pierre's stylesheet unconditionally paints 8px of padding under a file's last code line (--diffs-gap-fallback), but StyledDiffCodeView declared itemMetrics.paddingBottom: 0, so every expanded file's virtual height ran 8px short of its rendered height and the virtualizer's scroll range came up short by 8px per expanded file. Counting the painted 8px in the metric restores the pairing; spacing and paddingTop stay zero, so the gap above the first expanded file's header that the zeroing originally fixed does not come back. The thread diff panel shares this adapter and gets the same correction.

Validated in the running app against a live 10-file pull request: with one file or all files expanded (context hydration settled), the scroll range matches the rendered content exactly — the last row lands flush at the viewport bottom, with no new gap above or between files. Web typecheck passes.

BEFORE:

AFTER:

🤖 Generated with Claude Code

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Note

Low Risk
Single geometry constant in the shared diff adapter with no auth, data, or API changes; regression risk is limited to diff list scrolling layout.

Overview
Fixes PR Code tab (and shared diff views) clipping file rows below expanded files by setting itemMetrics.paddingBottom to 8 in StyledDiffCodeView, matching Pierre’s always-painted --diffs-gap-fallback under each file’s last line.

Previously virtual row height was 8px short per expanded file, so scroll range ended early and later files were unreachable. spacing and paddingTop stay 0 so the fix for the gap above the first expanded header is unchanged. The unit test expectation for paddingBottom is updated to 8.

^{Reviewed by Cursor Bugbot for commit 33d5a59. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Fix diff file list scrolling by correcting itemMetrics.paddingBottom in StyledDiffCodeView

The virtualized height calculation in StyledDiffCodeView was not accounting for the 8px bottom padding painted by the stylesheet, causing the last rows of expanded files to be clipped and the end of the list to be unreachable via scrolling. Sets itemMetrics.paddingBottom from 0 to 8 in StyledDiffCodeView.tsx to match the actual rendered gap.

^{Macroscope summarized 33d5a59.}

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[macroscopeapp]

Approvability

Verdict: Approved 33d5a59

This is a straightforward UI bug fix that corrects a scroll calculation error by adjusting a padding metric from 0 to 8 pixels. The change is minimal, well-documented with a clear comment explaining the root cause, and includes an updated test.

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