feat(format): add token count formatting utility

Add formatTokenCount utility function to format large numbers with K/M suffixes for display.

- Converts 32000 -> "32K"
- Converts 128000 -> "128K"
- Converts 1000000 -> "1M"
- Handles edge cases and removes trailing .0 decimals

This utility provides consistent formatting for token counts across the application UI.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: ericyangpan

src/lib/format.ts

@@ -0,0 +1,24 @@
+/**
+ * Formatting utility functions
+ */
+
+/**
+ * Format a large number with K/M suffix for display
+ * Examples:
+ * - 32000 -> "32K"
+ * - 128000 -> "128K"
+ * - 200000 -> "200K"
+ * - 1000000 -> "1M"
+ * - 4096 -> "4K"
+ * @param value - The number to format
+ * @returns Formatted string with K/M suffix
+ */
+export function formatTokenCount(value: number): string {
+  if (value >= 1000000) {
+    return `${(value / 1000000).toFixed(1)}M`.replace(/\.0$/, '')
+  }
+  if (value >= 1000) {
+    return `${(value / 1000).toFixed(1)}K`.replace(/\.0$/, '')
+  }
+  return value.toString()
+}