Standardize warning output to use style.PrintWarning (gt-g6kor)

- Add PrintWarning helper in internal/style/style.go
- Update 35 warning message outputs across 16 files to use consistent format
- All warnings now display as "⚠ Warning: <message>" in yellow/bold

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

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

internal/cmd/done.go

@@ -208,7 +208,7 @@ func runDone(cmd *cobra.Command, args []string) error {
 
 	fmt.Printf("\nNotifying Witness...\n")
 	if err := townRouter.Send(doneNotification); err != nil {
-		fmt.Printf("  %s\n", style.Dim.Render(fmt.Sprintf("Warning: could not notify witness: %v", err)))
+		style.PrintWarning("could not notify witness: %v", err)
 	} else {
 		fmt.Printf("%s Witness notified of %s\n", style.Bold.Render("✓"), exitType)
 	}