Add comma formatting to input and output token displays

The token counts now display with commas in both the terminal UI and web UI.

Co-Authored-By: sketch <hello@sketch.dev>
diff --git a/termui/termui.go b/termui/termui.go
index 32f3300..36e5701 100644
--- a/termui/termui.go
+++ b/termui/termui.go
@@ -16,6 +16,7 @@
 	"text/template"
 	"time"
 
+	"github.com/dustin/go-humanize"
 	"github.com/fatih/color"
 	"golang.org/x/term"
 	"sketch.dev/loop"
@@ -206,8 +207,8 @@
 		case "usage", "cost":
 			totalUsage := ui.agent.TotalUsage()
 			ui.AppendSystemMessage("💰 Current usage summary:")
-			ui.AppendSystemMessage("- Input tokens: %d", totalUsage.TotalInputTokens())
-			ui.AppendSystemMessage("- Output tokens: %d", totalUsage.OutputTokens)
+			ui.AppendSystemMessage("- Input tokens: %s", humanize.Comma(int64(totalUsage.TotalInputTokens())))
+			ui.AppendSystemMessage("- Output tokens: %s", humanize.Comma(int64(totalUsage.OutputTokens)))
 			ui.AppendSystemMessage("- Responses: %d", totalUsage.Responses)
 			ui.AppendSystemMessage("- Wall time: %s", totalUsage.WallTime().Round(time.Second))
 			ui.AppendSystemMessage("- Total cost: $%0.2f", totalUsage.TotalCostUSD)
@@ -216,8 +217,8 @@
 			// Display final usage stats
 			totalUsage := ui.agent.TotalUsage()
 			ui.AppendSystemMessage("💰 Final usage summary:")
-			ui.AppendSystemMessage("- Input tokens: %d", totalUsage.TotalInputTokens())
-			ui.AppendSystemMessage("- Output tokens: %d", totalUsage.OutputTokens)
+			ui.AppendSystemMessage("- Input tokens: %s", humanize.Comma(int64(totalUsage.TotalInputTokens())))
+			ui.AppendSystemMessage("- Output tokens: %s", humanize.Comma(int64(totalUsage.OutputTokens)))
 			ui.AppendSystemMessage("- Responses: %d", totalUsage.Responses)
 			ui.AppendSystemMessage("- Wall time: %s", totalUsage.WallTime().Round(time.Second))
 			ui.AppendSystemMessage("- Total cost: $%0.2f", totalUsage.TotalCostUSD)