feat(server): improve indexer perf (#15512)

#### PR Dependency Tree


* **PR #15512** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Search now supports generation-based indexing with embedded and remote
providers.
* Added automatic search reconciliation and improved handling of
document, workspace, and permission changes.
* Added clearer search status errors for unavailable, syncing, unready,
or failed indexes.
* Added Manticore Search end-to-end support and provider-specific search
behavior.

* **Improvements**
* Search and aggregate pagination now report returned results and
continuation status more accurately.
* Improved permission filtering to prevent inaccessible documents from
appearing in results.
  * Admin provider selection now consistently enables indexing.

* **Documentation**
* Clarified search pagination, aggregation counts, provider
configuration, and end-to-end setup.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/admin/src/modules/settings/index.tsx

@@ -175,9 +175,8 @@ const AdminPanel = ({
                     {fields.map(field => {
                       const fieldKey =
                         typeof field === 'string' ? field : String(field.key);
-                      const effectiveIndexerProvider = sourceConfig?.enabled
-                        ? sourceConfig?.provider?.type
-                        : 'embedded';
+                      const effectiveIndexerProvider =
+                        sourceConfig?.provider?.type ?? 'embedded';
                       if (
                         module === 'indexer' &&
                         effectiveIndexerProvider === 'embedded' &&
@@ -219,12 +218,8 @@ const AdminPanel = ({
                             module === 'indexer' &&
                             field.key === 'provider.type'
                               ? (_path, value) => {
-                                  if (value === 'embedded') {
-                                    onUpdate('indexer/enabled', false);
-                                  } else {
-                                    onUpdate('indexer/enabled', true);
-                                    onUpdate('indexer/provider.type', value);
-                                  }
+                                  onUpdate('indexer/enabled', true);
+                                  onUpdate('indexer/provider.type', value);
                                 }
                               : onUpdate,
                         };