Make changing engine-run code superuser-only

Writing node source, installing modules and any flow save that adds,
retypes or repoints a code node (Function, Command), edits a Command
node's settings or changes a node's resources.env now answer 403 for
everyone but a superuser. MCP tools and the assistant reach the same
routes, so they inherit the gate. Node types report runs_code.

The editor shows code read-only with a note, disables a Command node's
settings, leaves code nodes and reusable nodes out of the palette and
paste, and the Modules page offers no install.

frontend/src/client/schemas.gen.ts

@@ -2573,6 +2573,11 @@ export const NodeTypeInfoSchema = {
             title: 'Has Source',
             default: false
         },
+        runs_code: {
+            type: 'boolean',
+            title: 'Runs Code',
+            default: false
+        },
         free_params: {
             type: 'boolean',
             title: 'Free Params',

frontend/src/client/sdk.gen.ts

@@ -1478,6 +1478,8 @@ export class ModulesService {
      * Apply Modules
      * Install exactly these requirements, then hand them to the workers.
      *
+     * A superuser's: a package runs its own code on install and on import.
+     *
      * A manifest that does not resolve changes nothing: the venv is left as it
      * was and the stored manifest is only written once the install succeeded.
      *

frontend/src/client/types.gen.ts

@@ -888,6 +888,7 @@ export type NodeTypeInfo = {
         [key: string]: unknown;
     };
     has_source?: boolean;
+    runs_code?: boolean;
     free_params?: boolean;
     plugin?: (string | null);
 };