feat: add diagnostics and safe reset maintenance

internal/shell/shell.go

@@ -14,6 +14,8 @@ import (
 	"path/filepath"
 	"strings"
 
+	"golang.org/x/sys/unix"
+
 	"proxyctl/internal/profile"
 	"proxyctl/internal/securefs"
 	"proxyctl/internal/target"
@@ -187,6 +189,46 @@ func (a *Adapter) EnvironmentPath() string { return a.configuration.EnvironmentF
 func (a *Adapter) RecoveryPath() string    { return a.configuration.RecoveryFile }
 func (a *Adapter) StartupPath() string     { return a.configuration.StartupFile }
 
+// DiagnosticChecks performs no writes or command execution.
+func (a *Adapter) DiagnosticChecks(_ context.Context, _ *profile.Profile) []target.Check {
+	paths := []string{a.configuration.EnvironmentFile, a.configuration.RecoveryFile}
+	writable := true
+	var evidence []string
+	for _, path := range paths {
+		ok, detail := writablePath(path)
+		writable = writable && ok
+		evidence = append(evidence, detail)
+	}
+	return []target.Check{
+		{Name: "required commands", OK: true, Evidence: "Shell Target requires no external commands"},
+		{Name: "write authority", OK: writable, Evidence: strings.Join(evidence, "; ")},
+	}
+}
+
+func writablePath(path string) (bool, string) {
+	candidate := path
+	for {
+		info, err := os.Stat(candidate)
+		if err == nil {
+			if !info.IsDir() {
+				candidate = filepath.Dir(candidate)
+			}
+			if err := unix.Access(candidate, unix.W_OK); err != nil {
+				return false, candidate + " is not writable: " + err.Error()
+			}
+			return true, candidate + " is writable"
+		}
+		if !errors.Is(err, fs.ErrNotExist) {
+			return false, candidate + " cannot be inspected: " + err.Error()
+		}
+		parent := filepath.Dir(candidate)
+		if parent == candidate {
+			return false, path + " has no writable existing ancestor"
+		}
+		candidate = parent
+	}
+}
+
 func (a *Adapter) Inspect(_ context.Context, active *profile.Profile) target.Inspection {
 	metadata, managed, metadataErr := a.readRecovery()
 	generated, generatedErr := a.files.ReadFile(a.configuration.EnvironmentFile)