Replace deprecated io/ioutil with os package

- Replace ioutil.ReadFile with os.ReadFile
- Replace ioutil.ReadDir with os.ReadDir
- Remove io/ioutil imports
- All tests passing

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

Author: aurc

internal/reader/types.go

@@ -24,7 +24,6 @@ package reader
 
 import (
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path"
 	"sort"
@@ -161,7 +160,7 @@ func List() ([]*SavedParamsWrapper, error) {
 	if err != nil {
 		return nil, err
 	}
-	files, err := ioutil.ReadDir(paramsDir)
+	files, err := os.ReadDir(paramsDir)
 	if err != nil {
 		return nil, err
 	}

internal/uitest/helper/json_gen.go

@@ -26,15 +26,15 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"math/rand"
+	"os"
 	"time"
 
 	"github.com/google/uuid"
 )
 
 func JsonGenerator(writer io.Writer) {
-	b, err := ioutil.ReadFile("internal/testdata/test1.json")
+	b, err := os.ReadFile("internal/testdata/test1.json")
 	if err != nil {
 		panic(err)
 	}

internal/uitest/helper/json_gen/main.go

@@ -25,7 +25,6 @@ package main
 import (
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
 	"math/rand"
 	"os"
 	"time"
@@ -37,7 +36,7 @@ import (
 const datelayout = "2006-01-02T15:04:05-0700"
 
 func main() {
-	b, err := ioutil.ReadFile("internal/testdata/test1.json")
+	b, err := os.ReadFile("internal/testdata/test1.json")
 	if err != nil {
 		panic(err)
 	}