Harden core snapshot sync and workspace lifecycle

internal/core/files/path_policy.go

@@ -25,8 +25,7 @@ func IsReservedPath(relativePath string) bool {
 	if cleaned == "" {
 		return false
 	}
-	first := strings.Split(cleaned, "/")[0]
-	return strings.EqualFold(first, ".verstak")
+	return containsReservedSegment(cleaned)
 }
 
 func normalizeRelativePath(input string, allowRoot bool) (string, error) {
@@ -67,8 +66,16 @@ func IsReservedPathNoNormalize(cleaned string) bool {
 	if cleaned == "" {
 		return false
 	}
-	first := strings.Split(cleaned, "/")[0]
-	return strings.EqualFold(first, ".verstak")
+	return containsReservedSegment(cleaned)
+}
+
+func containsReservedSegment(cleaned string) bool {
+	for _, segment := range strings.Split(cleaned, "/") {
+		if strings.EqualFold(segment, ".verstak") {
+			return true
+		}
+	}
+	return false
 }
 
 func looksAbsolute(input string) bool {

internal/core/files/path_policy_test.go

@@ -43,6 +43,7 @@ func TestNormalizeRelativeFileRejectsUnsafePaths(t *testing.T) {
 		".verstak/vault.json",
 		"./.verstak",
 		".verstak/trash",
+		"Workspace/.verstak/workspace.json",
 		"folder/../.verstak",
 		".Verstak",
 	}
@@ -70,6 +71,9 @@ func TestReservedPathPolicy(t *testing.T) {
 	if IsReservedPath("Notes/.verstak.md") {
 		t.Fatal("Notes/.verstak.md should not be reserved")
 	}
+	if !IsReservedPath("Workspace/.verstak/workspace.json") {
+		t.Fatal("nested .verstak should be reserved")
+	}
 }
 
 func TestNormalizeRelativeFileAcceptsOnlySlashSeparatedRelativePaths(t *testing.T) {