Group changed files in the Changes view into a collapsible directory
tree instead of a flat list, on every form factor — consistent with the
Files explorer, which already renders a directory tree on mobile.
Folders are collapsible and expanded by default, single-child directory
chains are compressed into one row (packages/app/src), and folder rows
show aggregate +/- stats.
Client-only, built entirely from the existing ParsedDiffFile paths:
- diff-tree.ts: pure build/compress/flatten of the directory hierarchy,
keyed by full uncompressed dir path so collapse state survives
compression changes as the diff mutates.
- diff-flat-items.ts: pure buildDiffFlatItems + sumHeightsBefore. The
function retains a flat mode (showTree=false) as a tested seam for a
possible future flat/tree toggle; sticky header indices are
file-headers-only, derived from the post-collapse list.
- panel-store: diffCollapsedFoldersByWorkspace slice (collapsed-set, so
folders default to expanded), persisted via version 12. The set is
reconciled against the current diff so folders that leave and reappear
default to expanded and the stored set stays bounded.
Presentation primitives (chevron, indent guides, indent constant) are
extracted into components/tree-primitives and shared with the Files
explorer, which drops its private copies (and a banned useUnistyles
call site). The two trees now render identical rows; only the
tree-building stays separate (server listings vs. diff paths).
The toolbar's expand-all stays file-diffs-only (renamed
allFileDiffsExpanded); a separate control collapses/expands all folders.
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
