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/KeyboardShortcuts.tsx

@@ -51,7 +51,6 @@ export enum KeyboardAction {
   NEW_COLLECTION = "NEW_CONTAINER",
   NEW_ITEM = "NEW_ITEM",
   DELETE_ITEM = "DELETE_ITEM",
-  TOGGLE_COPILOT = "TOGGLE_COPILOT",
   SELECT_LEFT_TAB = "SELECT_LEFT_TAB",
   SELECT_RIGHT_TAB = "SELECT_RIGHT_TAB",
   CLOSE_TAB = "CLOSE_TAB",
@@ -82,7 +81,6 @@ const bindings: Record<KeyboardAction, string[]> = {
   [KeyboardAction.NEW_COLLECTION]: ["Alt+N C"],
   [KeyboardAction.NEW_ITEM]: ["Alt+N I"],
   [KeyboardAction.DELETE_ITEM]: ["Alt+D"],
-  [KeyboardAction.TOGGLE_COPILOT]: ["$mod+P"],
   [KeyboardAction.SELECT_LEFT_TAB]: ["$mod+Alt+BracketLeft", "$mod+Shift+F6"],
   [KeyboardAction.SELECT_RIGHT_TAB]: ["$mod+Alt+BracketRight", "$mod+F6"],
   [KeyboardAction.CLOSE_TAB]: ["$mod+Alt+W"],