fix(client): promote file tree node to directory when path is both file and directory prefix

[shimpeiws]

Summary

• Fix buildFileTree to promote an existing leaf node to a directory when a later file uses the same path as a directory prefix
• When a diff contains e.g. vendor (deleted file) and vendor/lib.ts (added file), the tree now correctly shows both entries

Fixes #452

Test plan

• Added test: path exists both as a file and a directory prefix — children are visible
• All existing tests pass (pnpm test — 840 passed)
• pnpm check and pnpm build pass

[yoshiko-pg]

Thanks for the fix! One issue with the promotion approach: a promoted node is rendered only as a directory in renderTreeNode, so the file row for the deleted vendor entry disappears from the tree. You lose click-to-scroll, the reviewed checkbox, and the comment count for that file. The test passes because getByTitle('vendor') matches the directory header title. The reverse order (vendor/lib.ts first, then vendor) also drops the file, since the existing directory node never gets file assigned.

An alternative that handles both orders and keeps the file row: treat the file and the directory as separate sibling nodes by matching on kind in the lookup, e.g. current.children.find((c) => c.name === part && c.isDirectory === !isLast). Note the directory node would then need a distinct React key since both nodes share the path vendor.

[shimpeiws]

@yoshiko-pg

Thanks for the review! Updated to the sibling node approach as you suggested.

Changes:

• buildFileTree: Added c.isDirectory === !isLast to the find condition so that a file node and a directory node with the same name coexist as separate siblings. Removed the promotion else if block entirely.
• renderTreeNode: Changed file row key to file:${file.path} to avoid duplicate React keys when both nodes exist.
• Test: Strengthened to verify that vendor appears as a clickable data-file-row element (not just a directory header) and that onScrollToFile is called on click.

[yoshiko-pg]

@shimpeiws Thank you!!