feat(container): migrate filesystem operations to io.Local abstraction

Migrate state.go:
- os.ReadFile → io.Local.Read
- os.MkdirAll → io.Local.EnsureDir
- os.WriteFile → io.Local.Write

Migrate templates.go:
- os.Stat → io.Local.IsFile/IsDir
- os.ReadFile → io.Local.Read
- os.ReadDir → io.Local.List

Part of #101 (io.Medium migration tracking issue).

Closes #108

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

pkg/container/state.go

@@ -5,6 +5,8 @@ import (
 	"os"
 	"path/filepath"
 	"sync"
+
+	"github.com/host-uk/core/pkg/io"
 )
 
 // State manages persistent container state.
@@ -56,7 +58,7 @@ func NewState(filePath string) *State {
 func LoadState(filePath string) (*State, error) {
 	state := NewState(filePath)
 
-	data, err := os.ReadFile(filePath)
+	dataStr, err := io.Local.Read(filePath)
 	if err != nil {
 		if os.IsNotExist(err) {
 			return state, nil
@@ -64,7 +66,7 @@ func LoadState(filePath string) (*State, error) {
 		return nil, err
 	}
 
-	if err := json.Unmarshal(data, state); err != nil {
+	if err := json.Unmarshal([]byte(dataStr), state); err != nil {
 		return nil, err
 	}
 
@@ -78,7 +80,7 @@ func (s *State) SaveState() error {
 
 	// Ensure the directory exists
 	dir := filepath.Dir(s.filePath)
-	if err := os.MkdirAll(dir, 0755); err != nil {
+	if err := io.Local.EnsureDir(dir); err != nil {
 		return err
 	}
 
@@ -87,7 +89,7 @@ func (s *State) SaveState() error {
 		return err
 	}
 
-	return os.WriteFile(s.filePath, data, 0644)
+	return io.Local.Write(s.filePath, string(data))
 }
 
 // Add adds a container to the state and persists it.
@@ -166,5 +168,5 @@ func EnsureLogsDir() error {
 	if err != nil {
 		return err
 	}
-	return os.MkdirAll(logsDir, 0755)
+	return io.Local.EnsureDir(logsDir)
 }

pkg/container/templates.go

@@ -7,6 +7,8 @@ import (
 	"path/filepath"
 	"regexp"
 	"strings"
+
+	"github.com/host-uk/core/pkg/io"
 )
 
 //go:embed templates/*.yml
@@ -71,12 +73,12 @@ func GetTemplate(name string) (string, error) {
 	userTemplatesDir := getUserTemplatesDir()
 	if userTemplatesDir != "" {
 		templatePath := filepath.Join(userTemplatesDir, name+".yml")
-		if _, err := os.Stat(templatePath); err == nil {
-			content, err := os.ReadFile(templatePath)
+		if io.Local.IsFile(templatePath) {
+			content, err := io.Local.Read(templatePath)
 			if err != nil {
 				return "", fmt.Errorf("failed to read user template %s: %w", name, err)
 			}
-			return string(content), nil
+			return content, nil
 		}
 	}
 
@@ -194,7 +196,7 @@ func getUserTemplatesDir() string {
 	cwd, err := os.Getwd()
 	if err == nil {
 		wsDir := filepath.Join(cwd, ".core", "linuxkit")
-		if info, err := os.Stat(wsDir); err == nil && info.IsDir() {
+		if io.Local.IsDir(wsDir) {
 			return wsDir
 		}
 	}
@@ -206,7 +208,7 @@ func getUserTemplatesDir() string {
 	}
 
 	homeDir := filepath.Join(home, ".core", "linuxkit")
-	if info, err := os.Stat(homeDir); err == nil && info.IsDir() {
+	if io.Local.IsDir(homeDir) {
 		return homeDir
 	}
 
@@ -217,7 +219,7 @@ func getUserTemplatesDir() string {
 func scanUserTemplates(dir string) []Template {
 	var templates []Template
 
-	entries, err := os.ReadDir(dir)
+	entries, err := io.Local.List(dir)
 	if err != nil {
 		return templates
 	}
@@ -266,12 +268,12 @@ func scanUserTemplates(dir string) []Template {
 // extractTemplateDescription reads the first comment block from a YAML file
 // to use as a description.
 func extractTemplateDescription(path string) string {
-	content, err := os.ReadFile(path)
+	content, err := io.Local.Read(path)
 	if err != nil {
 		return ""
 	}
 
-	lines := strings.Split(string(content), "\n")
+	lines := strings.Split(content, "\n")
 	var descLines []string
 
 	for _, line := range lines {