## 1. Implementation

- [x] 1.1 Create `client/cmd/reindex.go` with `kb reindex` command, `--yes`/`-y` flag, confirmation prompt matching `remove.go` pattern
- [x] 1.2 POST to `/api/v1/reindex`, handle human output (`Reindexed N chunks (model: ...)`) and JSON output
- [x] 1.3 Verify build compiles and command appears in `kb --help`