Fix 5 pre-existing web lint errors
- DeleteFolderConfirmDialog: remove redundant <DescendantCounts> type arg
and unused DescendantCounts interface
- TopBar: remove stale @typescript-eslint/unbound-method disable comment
- chapter.tsx: remove redundant <string> type arg from createContext
- pair.accept.lazy.tsx: add isLoading to handleApprove useCallback deps
- pair.request.lazy.tsx: convert let activePairInit to const ref-object
(satisfies functional/no-let while preserving reset semantics)