Fix delete-script FK error; trigger drift on scope change

- deleteScript: null out deployments.script_id/script_version_id/prior_version_id
  and deployment_scripts.prior_version_id inside a transaction before the
  cascade. These are historical audit FKs (NO ACTION), so the cascade from
  script_versions was blowing up any delete of a promoted script.
- Scope endpoint fires runDriftDeployment in the background after any scope
  mutation so orphan/missing files from the change get reconciled.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/lib/server/fleet/scripts.ts

@@ -337,7 +337,39 @@ export function deleteScript(scriptId: number): void {
         )
         .get(scriptId) as { id: number } | undefined;
     if (beta) throw new ScriptError(`beta ${beta.id} is still running against this script`, 'has-active-beta');
-    db().prepare('DELETE FROM scripts WHERE id = ?').run(scriptId);
+
+    // Null out deployment-history FKs that would otherwise block the cascade.
+    // deployments.script_id/script_version_id/prior_version_id and
+    // deployment_scripts.prior_version_id are historical audit references
+    // with no ON DELETE action; keep the deployment rows intact but drop
+    // the FK to the script so we can remove it.
+    const handle = db();
+    const tx = handle.transaction((id: number) => {
+        handle
+            .prepare(
+                `UPDATE deployments
+                    SET script_version_id = NULL
+                  WHERE script_version_id IN (SELECT id FROM script_versions WHERE script_id = ?)`
+            )
+            .run(id);
+        handle
+            .prepare(
+                `UPDATE deployments
+                    SET prior_version_id = NULL
+                  WHERE prior_version_id IN (SELECT id FROM script_versions WHERE script_id = ?)`
+            )
+            .run(id);
+        handle.prepare('UPDATE deployments SET script_id = NULL WHERE script_id = ?').run(id);
+        handle
+            .prepare(
+                `UPDATE deployment_scripts
+                    SET prior_version_id = NULL
+                  WHERE prior_version_id IN (SELECT id FROM script_versions WHERE script_id = ?)`
+            )
+            .run(id);
+        handle.prepare('DELETE FROM scripts WHERE id = ?').run(id);
+    });
+    tx(scriptId);
 }
 
 // Servers that match a script's scope. Empty for unscoped scripts — those are