feat: init command, README, fix config creation, move cicd

- cmd_init.go: interactive setup wizard (gosleep-timer init)
- README.md: comprehensive documentation
- config/config.go: fix os.IsNotExist → errors.Is for wrapped err
- main.go: remove '(no TUI)' from run help
- cicd.yaml moved to .github/workflows/cicd.yaml

main.go

@@ -319,7 +319,7 @@ func init() {
 
 	runCmd := &cobra.Command{
 		Use:   "run [duration]",
-		Short: "Run timer in CLI mode (no TUI)",
+		Short: "Run timer in CLI mode",
 		Args:  cobra.MaximumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			cliMode = true