Address two Greptile review comments:
1. Collapsed parent badge now shows total descendant count at all depths
rather than direct-child count only. Add `countDescendants` utility to
issue-tree.ts (recursive, uses existing childMap) and replace
`children.length` with it in the titleSuffix badge.
2. Add a useEffect that prunes stale IDs from `collapsedParents` whenever
the issues prop changes. Deleted or reassigned issues previously left
orphan IDs in localStorage indefinitely; the effect filters to only IDs
that appear as a parentId in the current issue list and persists the
cleaned array via updateView.
Add four unit tests for countDescendants: leaf node, single-level,
multi-level, and unknown ID.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
Extract the inline tree-building logic from IssuesList into a pure
`buildIssueTree` function in lib/issue-tree.ts so it can be unit tested.
Add six tests covering: flat lists, parent-child grouping, multi-level
nesting, orphaned sub-tasks promoted to root, empty input, and list
order preservation.
Add two tests to IssueRow.test.tsx covering the new titleSuffix prop:
renders inline after the title when provided, and renders cleanly when
omitted.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
