fix: finish progressive Target detection

internal/shell/shell_test.go

@@ -80,6 +80,24 @@ func TestShellDiagnosticsRejectSymlinkedPathsWithoutTouchingVictim(t *testing.T)
 	}
 }
 
+func TestDetectClassifiesMalformedRecoveryMetadataAsFailure(t *testing.T) {
+	a := newAdapter(t, "/bin/bash", nil)
+	if err := os.MkdirAll(filepath.Dir(a.RecoveryPath()), 0o700); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(a.RecoveryPath(), []byte("{malformed"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	detection := a.Detect(context.Background(), activeProfile())
+	if detection.Err == nil || detection.Inspection.State != target.Drifted {
+		t.Fatalf("detection = %#v, want failed Drifted inspection", detection)
+	}
+	if got := a.Inspect(context.Background(), activeProfile()); got.State != target.Drifted {
+		t.Fatalf("maintenance inspection = %#v, want established Drifted semantics", got)
+	}
+}
+
 func TestShellAvailabilitySupportsOnlyBashAndZsh(t *testing.T) {
 	for _, tc := range []struct {
 		shell     string