[datlechin]

Summary

• Open Quickly keeps its panel and view tree between opens. The next Cmd-Shift-O swaps in a new QuickSwitcherViewModel instead of building an NSPanel and NSHostingController and measuring them at a full-screen proposal.
• QuickSwitcherPanelController.present takes retainsPanel. Jump to Column, the toolbar switchers and the recent tab switcher still get a fresh panel, released on close.
• QuickSwitcherPanelView takes its model from the caller, and its loads are keyed by the model, so a swapped model loads on its own.
• Closing runs QuickSwitcherViewModel.releaseResults(): the hidden model drops its results, stops observing the catalog, and its in-flight loads drop what they bring.
• The panel's key commands are installed on every update. WindowAccessor installed them only once, which would have left them on the previous model.
• The sidebar no longer reloads every row when an all-schema table listing lands while its search is empty. DatabaseTreeRenderInputs leaves the listing out without a search, since the outline reads it only under one. Open Quickly requests that listing on Oracle and PostgreSQL, and its landing was a 100 ms-plus turn of sidebar row layout.

Test plan

• New: QuickSwitcherPanelControllerTests.retainedPanelSwapsItsModel checks that reopening returns the same window, sends Cmd-2 to the new model and releases the old one. QuickSwitcherViewModelTests.releasedModelDropsResults checks that a released model is empty and ignores a later load and search.
• Unchanged: closingReleasesTheViewModel still covers the non-retained path.
• Changed on purpose: DatabaseTreeReconcileTests.listingStartingToLoadIsNoChange now passes a search, and checks that a landing with an empty search leaves the inputs equal.
• Local: the Quick Switcher, DatabaseTree*, HierarchicalSchemaSearch and SidebarOutlineScaffold suites (361 tests) pass; lint clean.
• Release build with Time Profiler attached against main, 4 opens per fixture. These are the main thread's CPU samples per warm open, at 1 ms each. They were measured on a build of the same panel path before release on close was added:

Fixture	main	this branch
MySQL	64-82	48-59
PostgreSQL	58-66	38-40
Oracle	80-152	48-66

• The first open after launch is unchanged, at 114 to 154 samples.
• Load was 40 to 560 from other sessions' builds and VMs, so wall-clock times are not comparable.
• Manual probe: a search field keeps its field editor across the panel's close() and reopen. Setting stringValue while editing keeps editing, so the field still has focus when the panel reopens.

Refs #3661