Reindex command, implicit note shorthand, add→addfile rename

- Add `kb reindex` command with confirmation prompt and --yes flag
- Add implicit note shorthand: `kb "my note"` submits a note directly
- Rename `add` to `addfile`, remove --note/--title/--type flags
- Add client-side file extension validation before upload
- Add `kb examples` command for common usage patterns
- Update README, SKILL.md, and main specs
- Archive completed changes and sync delta specs

BREAKING: `kb add` renamed to `kb addfile`, `kb add --note` replaced by `kb "text"`

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

client/cmd/reindex.go

@@ -0,0 +1,83 @@
+package cmd
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/kb-search/kb/internal/api"
+	"github.com/kb-search/kb/internal/output"
+	"github.com/spf13/cobra"
+)
+
+var reindexCmd = &cobra.Command{
+	Use:   "reindex",
+	Short: "Re-embed all chunks with the current engine model",
+	Args:  cobra.NoArgs,
+	RunE:  runReindex,
+}
+
+func init() {
+	reindexCmd.Flags().BoolP("yes", "y", false, "skip confirmation prompt")
+	rootCmd.AddCommand(reindexCmd)
+}
+
+func runReindex(cmd *cobra.Command, args []string) error {
+	yes, _ := cmd.Flags().GetBool("yes")
+
+	client := api.NewClient()
+
+	if !yes {
+		// Fetch model name from engine status
+		modelName := "current"
+		statusResp, err := client.Get("/api/v1/status")
+		if err == nil && api.CheckError(statusResp) == nil {
+			var status struct {
+				ModelName string `json:"model_name"`
+			}
+			if api.DecodeJSON(statusResp, &status) == nil && status.ModelName != "" {
+				modelName = status.ModelName
+			}
+		}
+
+		fmt.Printf("Reindex all chunks? This will re-embed everything with the %s model. [y/N] ", modelName)
+		reader := bufio.NewReader(os.Stdin)
+		answer, _ := reader.ReadString('\n')
+		answer = strings.TrimSpace(strings.ToLower(answer))
+		if answer != "y" && answer != "yes" {
+			fmt.Println("Cancelled.")
+			return nil
+		}
+	}
+	resp, err := client.Post("/api/v1/reindex", nil)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+	if err := api.CheckError(resp); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+
+	var result struct {
+		ChunksReindexed int    `json:"chunks_reindexed"`
+		Model           string `json:"model"`
+	}
+
+	if output.IsJSON() {
+		var raw interface{}
+		if err := api.DecodeJSON(resp, &raw); err != nil {
+			fmt.Fprintln(os.Stderr, "Failed to parse response:", err)
+			os.Exit(1)
+		}
+		output.PrintJSON(raw)
+	} else {
+		if err := api.DecodeJSON(resp, &result); err != nil {
+			fmt.Fprintln(os.Stderr, "Failed to parse response:", err)
+			os.Exit(1)
+		}
+		fmt.Printf("Reindexed %d chunks (model: %s)\n", result.ChunksReindexed, result.Model)
+	}
+	return nil
+}