feat(command): extend slash command system with new commands and UX improvements

Add 9 new command groups (/model, /memory, /search, /browser, /usage,
/email, /heartbeat, /skill, /fs) and improve existing commands by hiding
internal UUIDs, resolving IDs to human-readable names in /settings, and
switching /schedule to name-based references.

internal/command/formatter.go

@@ -0,0 +1,77 @@
+package command
+
+import (
+	"fmt"
+	"strings"
+)
+
+// formatItems renders a list of records as a Markdown-style list.
+// Each record is a slice of kv pairs; the first pair's value is used as the
+// bullet title, and subsequent pairs are indented beneath it.
+//
+// Example output:
+//
+//	- mybot
+//	  Description: A helpful assistant
+//	  ID: abc123
+//
+//	- another
+//	  Description: Something else
+//	  ID: def456
+func formatItems(items [][]kv) string {
+	if len(items) == 0 {
+		return ""
+	}
+	var b strings.Builder
+	for i, record := range items {
+		if len(record) == 0 {
+			continue
+		}
+		if i > 0 {
+			b.WriteByte('\n')
+		}
+		fmt.Fprintf(&b, "- %s\n", record[0].value)
+		for _, pair := range record[1:] {
+			fmt.Fprintf(&b, "  %s: %s\n", pair.key, pair.value)
+		}
+	}
+	return b.String()
+}
+
+// formatKV renders key-value pairs as a simple Markdown list.
+//
+// Example output:
+//
+//	- ID: abc123
+//	- Name: mybot
+func formatKV(pairs []kv) string {
+	var b strings.Builder
+	for _, p := range pairs {
+		fmt.Fprintf(&b, "- %s: %s\n", p.key, p.value)
+	}
+	return b.String()
+}
+
+type kv struct {
+	key   string
+	value string
+}
+
+// truncate shortens a string to maxLen, appending "..." if truncated.
+func truncate(s string, maxLen int) string {
+	if len(s) <= maxLen {
+		return s
+	}
+	if maxLen <= 3 {
+		return s[:maxLen]
+	}
+	return s[:maxLen-3] + "..."
+}
+
+// boolStr returns "yes" or "no".
+func boolStr(b bool) string {
+	if b {
+		return "yes"
+	}
+	return "no"
+}