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

config/config.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"os/exec"
@@ -70,7 +71,7 @@ func LoadOrCreate(path string) (*Config, error) {
 		return cfg, nil
 	}
 
-	if !os.IsNotExist(err) {
+	if !errors.Is(err, os.ErrNotExist) {
 		return nil, err
 	}