fix(commits): scroll changed-files list in graph commit detail (DAN-79)

[danielss-dev]

Linear

DAN-79 — All Commits graph commit detail: changed-files list cannot scroll.

Problem

The right-hand commit detail panel lists changed files in the upper vertical split (.cd-files inside a react-resizable-panels Panel). That host was flex-shrink: 0 with no height fill and no overflow-y, so a commit that touched more files than fit clipped instead of scrolling. Files below the visible rows were unreachable; the header and diff stayed on screen.

This is the same react-resizable-panels trap in docs/learnings.md: Panel children are display: block, so they need height: 100% (not leftover flex shrink) plus min-height: 0 and overflow-y: auto.

Fix

Smallest CSS/layout change; no second file-list UI.

• .cd-files: height: 100%, min-height: 0, overflow-y: auto; drop flex-shrink: 0
• .cd-diff / .cd-diff-scroll: fill the lower panel with the same scroll-host pattern as Local Changes (.lc-diff-scroll) so the diff still scrolls independently
• PanelResizeHandle class rs-handle horiz so the row-resize hit area matches other vertical splits

File-row selection, active styling, header actions, empty/loading states, and Pierre text/image diffs are unchanged.

Tests

No existing suite covers commit-detail chrome, so this PR does not add a layout CSS test. Manual check:

1. Open All Commits, select a commit with more changed files than fit in the upper pane (or shrink that pane via the resize handle).
2. Scroll the file list; every path can be focused.
3. Click a scrolled-into-view file; the diff below updates.
4. Scroll the diff pane; drag the vertical split; Checkout / Cherry-pick / Revert / stash actions and empty/loading states still work.

Proof

• pnpm --filter ./ui exec tsc --noEmit — pass
• pnpm --filter ./ui test — 99 files / 568 tests pass
• Demo harness (?view=commits, padded to 49 paths so the list exceeds the upper pane): .cd-files is overflow-y: auto, clientHeight 190 vs scrollHeight 1290, scrollTop 1100 after jumping to the last path. Clicking that path sets .cd-file.active and swaps the diff. Dragging .rs-handle.horiz (9px) grew the file pane 190 → 270px; the list stayed scrollable. Header still showed Checkout / Cherry-pick / Revert.

The Linear issue already has the before screenshot (list squeezed, later paths unreachable). After:

Top of the overflowing list (header + split + diff still present):

Commit detail: changed-files list fills the upper pane and overflows

Scrolled to the last path; selecting it updates the diff:

Commit detail: scrolled file list with last path selected

Selecting the original file again restores the text diff:

Commit detail: reselecting the first file restores the Pierre diff

Media is not committed on the branch.

Out of scope

Virtualizing huge file lists, redesigning commit-detail IA, pending/local Changes file lists.

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