Perf/copilot cleanup and optimizations (#2447)

* perf: remove deprecated copilot feature, add ARM timeouts, fix race conditions

- Remove entire QueryCopilot feature (~50 files deleted, ~30 files cleaned)
- Remove CopilotConfigured and SampleDataLoaded metric phases
- Fix DatabaseTreeRendered 76% stuck rate (remove one-shot guard in useMetricPhases)
- Add 8s default timeout to ARM requests (AbortController-based)
- Fix MSAL token forceRefresh (true -> false, use cache)
- Add concurrency limit of 5 to collection loading in Explorer
- Remove orphaned SampleDataClient.ts and queryCopilotSampleData.json
- Clean up dead sampleDataConnectionInfo field from UserContext

* Clean up copilot and optimize initialization

* Clean up copilot and optimize initialization

src/Explorer/Tree/ResourceTree.tsx

@@ -10,16 +10,11 @@ import { ArrowSortDown20Regular, ArrowSortUp20Regular, Home16Regular, Search20Re
 import { AuthType } from "AuthType";
 import { useTreeStyles } from "Explorer/Controls/TreeComponent/Styles";
 import { TreeNode, TreeNodeComponent } from "Explorer/Controls/TreeComponent/TreeNodeComponent";
-import {
-  createDatabaseTreeNodes,
-  createResourceTokenTreeNodes,
-  createSampleDataTreeNodes,
-} from "Explorer/Tree/treeNodeUtil";
+import { createDatabaseTreeNodes, createResourceTokenTreeNodes } from "Explorer/Tree/treeNodeUtil";
 import { useDatabases } from "Explorer/useDatabases";
 import { useSelectedNode } from "Explorer/useSelectedNode";
 import { isFabricMirrored } from "Platform/Fabric/FabricUtil";
 import { userContext } from "UserContext";
-import { useQueryCopilot } from "hooks/useQueryCopilot";
 import { ReactTabKind, useTabs } from "hooks/useTabs";
 import * as React from "react";
 import { useEffect, useMemo } from "react";
@@ -67,10 +62,6 @@ export const ResourceTree: React.FC<ResourceTreeProps> = ({ explorer }: Resource
   const sortOrder = useDatabases((state) => state.sortOrder);
   const setSortOrder = useDatabases((state) => state.setSortOrder);
   const pinnedDatabaseIds = useDatabases((state) => state.pinnedDatabaseIds);
-  const { isCopilotEnabled, isCopilotSampleDBEnabled } = useQueryCopilot((state) => ({
-    isCopilotEnabled: state.copilotEnabled,
-    isCopilotSampleDBEnabled: state.copilotSampleDBEnabled,
-  }));
 
   const databaseTreeNodes = useMemo(() => {
     return userContext.authType === AuthType.ResourceToken
@@ -94,18 +85,6 @@ export const ResourceTree: React.FC<ResourceTreeProps> = ({ explorer }: Resource
     pinnedDatabaseIds,
   ]);
 
-  const isSampleDataEnabled =
-    isCopilotEnabled &&
-    isCopilotSampleDBEnabled &&
-    userContext.sampleDataConnectionInfo &&
-    userContext.apiType === "SQL";
-
-  const sampleDataNodes = useMemo<TreeNode[]>(() => {
-    return isSampleDataEnabled && sampleDataResourceTokenCollection
-      ? createSampleDataTreeNodes(sampleDataResourceTokenCollection)
-      : [];
-  }, [isSampleDataEnabled, sampleDataResourceTokenCollection]);
-
   const headerNodes: TreeNode[] = isFabricMirrored()
     ? []
     : [
@@ -124,27 +103,10 @@ export const ResourceTree: React.FC<ResourceTreeProps> = ({ explorer }: Resource
       ];
 
   const rootNodes: TreeNode[] = useMemo(() => {
-    if (sampleDataNodes.length > 0) {
-      return [
-        ...headerNodes,
-        {
-          id: "data",
-          label: MY_DATA_TREE_LABEL,
-          children: databaseTreeNodes,
-          isScrollable: true,
-        },
-        {
-          id: "sampleData",
-          label: SAMPLE_DATA_TREE_LABEL,
-          children: sampleDataNodes,
-        },
-      ];
-    } else {
-      return [...headerNodes, ...databaseTreeNodes];
-    }
+    return [...headerNodes, ...databaseTreeNodes];
     // headerNodes is intentionally excluded — it depends only on isFabricMirrored() which is stable.
     // eslint-disable-next-line react-hooks/exhaustive-deps
-  }, [databaseTreeNodes, sampleDataNodes]);
+  }, [databaseTreeNodes]);
 
   // Track complete DatabaseLoad scenario (start, tree rendered, interactive)
   useDatabaseLoadScenario(databaseTreeNodes, databasesFetchedSuccessfully);