feat: add CLI commands for usage analysis, cost breakdown, and setup

Implement the complete Cobra command tree (11 subcommands):

- cmd/root.go: Root command with persistent flags (--days, --project,
  --model, --no-cache, --data-dir, --quiet, --no-subagents). Shared
  loadData() orchestrates the full pipeline: tries cache-assisted
  loading first, falls back to uncached parse on cache failure,
  reports progress to stderr. applyFilters() applies project/model
  substring filters and computes the time window.

- cmd/summary.go: Default command (also "cburn summary"). Renders a
  bordered metrics table with token breakdown (5 types), cost with
  cache savings, and per-day rates with period-over-period deltas.

- cmd/costs.go: Detailed cost analysis — breaks down costs by token
  type (output, cache_write_1h, input, cache_write_5m, cache_read)
  with share percentages, period comparison bar chart, and per-model
  cost breakdown (input/output/cache/total columns).

- cmd/daily.go: Daily usage table (date, weekday, sessions, prompts,
  tokens, cost) sorted most-recent-first.

- cmd/hourly.go: Activity heatmap showing prompt distribution across
  24 hours with Unicode block bars, reports peak hour.

- cmd/models.go: Model usage ranking with API call counts, token
  volumes, cost, and usage share percentage.

- cmd/projects.go: Project ranking by cost with session/prompt/token
  counts.

- cmd/sessions.go: Session list sorted by recency with --limit flag
  (default 20). Shows start time, project, duration, tokens, cost.
  Marks subagent sessions with "(sub)" suffix.

- cmd/config_cmd.go: Displays current configuration across all
  sections (general, admin API, appearance, budget) with auto-
  detected plan ceiling.

- cmd/setup.go: Interactive first-run wizard — configures Admin API
  key, default time range (7/30/90 days), and color theme (Flexoki
  Dark, Catppuccin Mocha, Tokyo Night, Terminal). Saves to
  ~/.config/cburn/config.toml.

- cmd/tui.go: Launches the interactive Bubble Tea TUI dashboard,
  passing through all filter flags and applying the configured theme.

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

cmd/sessions.go

@@ -0,0 +1,96 @@
+package cmd
+
+import (
+	"fmt"
+	"sort"
+
+	"cburn/internal/cli"
+	"cburn/internal/pipeline"
+
+	"github.com/spf13/cobra"
+)
+
+var sessionsCmd = &cobra.Command{
+	Use:   "sessions",
+	Short: "Session list with details",
+	RunE:  runSessions,
+}
+
+var sessionsLimit int
+
+func init() {
+	sessionsCmd.Flags().IntVarP(&sessionsLimit, "limit", "l", 20, "Number of sessions to show")
+	rootCmd.AddCommand(sessionsCmd)
+}
+
+func runSessions(_ *cobra.Command, _ []string) error {
+	result, err := loadData()
+	if err != nil {
+		return err
+	}
+	if len(result.Sessions) == 0 {
+		fmt.Println("\n  No sessions found.")
+		return nil
+	}
+
+	filtered, since, until := applyFilters(result.Sessions)
+	sessions := pipeline.FilterByTime(filtered, since, until)
+
+	if len(sessions) == 0 {
+		fmt.Println("\n  No sessions in the selected time range.")
+		return nil
+	}
+
+	// Sort by start time descending
+	sort.Slice(sessions, func(i, j int) bool {
+		return sessions[i].StartTime.After(sessions[j].StartTime)
+	})
+
+	// Limit
+	if sessionsLimit > 0 && len(sessions) > sessionsLimit {
+		sessions = sessions[:sessionsLimit]
+	}
+
+	fmt.Println()
+	fmt.Println(cli.RenderTitle(fmt.Sprintf("SESSIONS  Last %dd (showing %d)", flagDays, len(sessions))))
+	fmt.Println()
+
+	rows := make([][]string, 0, len(sessions))
+	for _, s := range sessions {
+		startStr := ""
+		if !s.StartTime.IsZero() {
+			startStr = s.StartTime.Local().Format("Jan 02 15:04")
+		}
+
+		totalTokens := s.InputTokens + s.OutputTokens +
+			s.CacheCreation5mTokens + s.CacheCreation1hTokens
+
+		project := s.Project
+		if s.IsSubagent {
+			project += " (sub)"
+		}
+
+		rows = append(rows, []string{
+			startStr,
+			truncate(project, 14),
+			cli.FormatDuration(s.DurationSecs),
+			cli.FormatTokens(totalTokens),
+			cli.FormatCost(s.EstimatedCost),
+		})
+	}
+
+	fmt.Print(cli.RenderTable(cli.Table{
+		Headers: []string{"Start", "Project", "Duration", "Tokens", "Cost"},
+		Rows:    rows,
+	}))
+
+	return nil
+}
+
+func truncate(s string, maxLen int) string {
+	runes := []rune(s)
+	if len(runes) <= maxLen {
+		return s
+	}
+	return string(runes[:maxLen-1]) + "…"
+}