fix(shell): add explicit return statements to functions

Add return 0 as the last statement in ~46 shell functions across
17 files that previously relied on implicit return codes
(SonarCloud rule shelldre:S7682).

scripts/create-wezterm-keymaps.sh

@@ -20,6 +20,7 @@ main()
   printf "\`\`\`\n\n- Generated on %s\n" "$(date)" >> "$DEST"
 
   msg "wezterm keybindings documentation generated at $DEST"
+  return 0
 }
 
 main "$@"