feat(manager-core): admin is implicit app_admin; delete-script needs AppAdmin

Aligns the canonical capability rules with how the dashboard now shadows
its UI. Instance admins become implicit app_admin on every app (only
InstanceManageSettings stays owner-only), and the script-delete handler
moves from AppWriteScript to AppAdmin so editors can save but not delete.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/manager-core/src/api.rs

@@ -270,10 +270,13 @@ async fn delete_script<R: ScriptRepository, L: ExecutionLogRepository>(
     Path(id): Path<ScriptId>,
 ) -> Result<StatusCode, ApiError> {
     let script = state.repo.get(id).await?.ok_or(ApiError::NotFound(id))?;
+    // Delete is gated tighter than Save: editors can edit scripts but
+    // only app_admin / instance admin / owner can remove them. See
+    // blueprint §11.6.
     require(
         state.authz.as_ref(),
         &principal,
-        Capability::AppWriteScript(script.app_id),
+        Capability::AppAdmin(script.app_id),
     )
     .await?;
     state.repo.delete(id).await?;