## Context

The engine's `POST /api/v1/reindex` re-embeds all chunks synchronously and returns `{"chunks_reindexed": N, "model": "..."}`. The client has an established confirmation pattern in `remove.go` using `--yes`/`-y` flag.

## Goals / Non-Goals

**Goals:**
- Add `kb reindex` with confirmation prompt matching `kb remove` pattern
- Display human-readable and JSON output

**Non-Goals:**
- Progress reporting during reindex (engine returns synchronously)
- Model selection from the client (model is engine-side config)

## Decisions

### 1. Confirmation prompt before reindex

Reindex drops and rebuilds the vector table — destructive if interrupted. Use the same `[y/N]` prompt pattern as `kb remove`, skippable with `--yes`/`-y`.

### 2. Warn that it may take a while

The prompt should mention that reindex re-embeds all chunks, so the user knows it's not instant.