feat: add CLI formatting utilities and table renderer

Implement the presentation layer for terminal output:

- cli/format.go: Human-readable formatting functions — FormatTokens
  (K/M/B suffixes), FormatCost (adaptive precision: $X.XX under $10,
  $X.X under $100, $X over $100, comma-separated over $1000),
  FormatDuration (Xh Ym / Xm / Xs), FormatNumber (comma-separated
  integers), FormatPercent (0-1 -> "XX.X%"), FormatDelta (signed
  cost delta with +/- prefix), FormatDayOfWeek (weekday number to
  3-letter abbreviation).

- cli/render.go: lipgloss-styled output components using the Flexoki
  Dark color palette:

  * RenderTitle: centered title in a rounded border box.

  * RenderTable: full-featured bordered table with auto-calculated
    column widths, right-aligned numeric columns (all except first),
    separator rows (triggered by "---" sentinel), and proper Unicode
    box-drawing characters. Supports optional title header and
    explicit column widths.

  * RenderProgressBar: bracketed fill bar with current/total counts.

  * RenderSparkline: Unicode block sparkline (8-level: ▁ through █)
    from arbitrary float64 series, auto-scaled to max.

  * RenderHorizontalBar: simple horizontal bar chart entry for
    inline comparisons.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/cli/format.go

@@ -0,0 +1,110 @@
+package cli
+
+import (
+	"fmt"
+	"math"
+	"strings"
+)
+
+// FormatTokens formats a token count with human-readable suffixes.
+// e.g., 1234 -> "1.2K", 1234567 -> "1.2M", 1234567890 -> "1.2B"
+func FormatTokens(n int64) string {
+	abs := n
+	if abs < 0 {
+		abs = -abs
+	}
+
+	switch {
+	case abs >= 1_000_000_000:
+		return fmt.Sprintf("%.1fB", float64(n)/1_000_000_000)
+	case abs >= 1_000_000:
+		return fmt.Sprintf("%.1fM", float64(n)/1_000_000)
+	case abs >= 1_000:
+		return fmt.Sprintf("%.1fK", float64(n)/1_000)
+	default:
+		return fmt.Sprintf("%d", n)
+	}
+}
+
+// FormatCost formats a USD cost value.
+func FormatCost(cost float64) string {
+	if cost >= 1000 {
+		return fmt.Sprintf("$%s", FormatNumber(int64(math.Round(cost))))
+	}
+	if cost >= 100 {
+		return fmt.Sprintf("$%.0f", cost)
+	}
+	if cost >= 10 {
+		return fmt.Sprintf("$%.1f", cost)
+	}
+	return fmt.Sprintf("$%.2f", cost)
+}
+
+// FormatDuration formats seconds into a human-readable duration.
+// e.g., 3725 -> "1h 2m", 125 -> "2m", 45 -> "45s"
+func FormatDuration(secs int64) string {
+	if secs <= 0 {
+		return "0s"
+	}
+
+	hours := secs / 3600
+	mins := (secs % 3600) / 60
+
+	if hours > 0 {
+		return fmt.Sprintf("%dh %dm", hours, mins)
+	}
+	if mins > 0 {
+		return fmt.Sprintf("%dm", mins)
+	}
+	return fmt.Sprintf("%ds", secs)
+}
+
+// FormatNumber adds comma separators to an integer.
+// e.g., 1234567 -> "1,234,567"
+func FormatNumber(n int64) string {
+	if n < 0 {
+		return "-" + FormatNumber(-n)
+	}
+
+	s := fmt.Sprintf("%d", n)
+	if len(s) <= 3 {
+		return s
+	}
+
+	var result strings.Builder
+	remainder := len(s) % 3
+	if remainder > 0 {
+		result.WriteString(s[:remainder])
+	}
+	for i := remainder; i < len(s); i += 3 {
+		if result.Len() > 0 {
+			result.WriteByte(',')
+		}
+		result.WriteString(s[i : i+3])
+	}
+	return result.String()
+}
+
+// FormatPercent formats a 0-1 float as a percentage string.
+func FormatPercent(f float64) string {
+	return fmt.Sprintf("%.1f%%", f*100)
+}
+
+// FormatDelta formats a cost delta with sign and color hint.
+// Returns the formatted string and whether it's positive.
+func FormatDelta(current, previous float64) string {
+	delta := current - previous
+	if delta >= 0 {
+		return fmt.Sprintf("+%s", FormatCost(delta))
+	}
+	return fmt.Sprintf("-%s", FormatCost(-delta))
+}
+
+// FormatDayOfWeek returns a 3-letter day abbreviation from a weekday number.
+func FormatDayOfWeek(weekday int) string {
+	days := []string{"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"}
+	if weekday >= 0 && weekday < 7 {
+		return days[weekday]
+	}
+	return "???"
+}