fix: harden preprocessing state and child capabilities

harness/tht/cli/schema_cmd.py

@@ -16,11 +16,11 @@ from tht.mschema.eligibility import classify_all
 schema_app = typer.Typer(help="Gestione mschema (rappresentazione canonica dello schema)")
 logger = logging.getLogger(__name__)
 
-def _require_writer_capability() -> None:
-    import os
-    if os.environ.get("THOTH_WORKSPACE_CAPABILITY_REQUIRED") == "1":
-        from tht.workspace_writer_lock import require_workspace_writer_capability
-        require_workspace_writer_capability()
+def _require_writer_capability(*, workspace_id: str | None = None, revision: str | None = None) -> None:
+    # Authorization is unconditional: an environment marker is attacker-controlled
+    # and must never turn a mutating direct invocation into an authorized child.
+    from tht.workspace_writer_lock import require_workspace_writer_capability
+    require_workspace_writer_capability(workspace_id=workspace_id, revision=revision)
 
 
 def _add_examples(dwh, phys, examples) -> None:
@@ -569,6 +569,7 @@ def suggest_fks_cmd(
         for item in payload["candidates"]
     }
     if write:
+        _require_writer_capability(workspace_id=getattr(getattr(cfg, "runtime_identity", None), "workspace_id", None), revision=getattr(getattr(cfg, "runtime_identity", None), "workspace_revision", None))
         for table_name, table_payload in candidate_tables.items():
             ann = annotations.tables.setdefault(table_name, TableAnnotation())
             from tht.mschema.models import ForeignKey