[datlechin]

Summary

• Open Quickly draws its results with one flat ForEach and no .id on a row. The nested ForEach(groups) { ForEach(items) } in a LazyVStack kept a row realized under a removed group (Tables, Recent) on screen once a search moved its item into the results, and never updated it: no highlight, no bold match, and a stale second highlight.
• New QuickSwitcherList owns that rule and the scrolling for Open Quickly, Jump to Column and the recent-tab switcher.
• A section header draws inside its group's first row, so arrowing back up shows it again.
• The list scrolls to the selection on each new search. A query whose best match was the scrolled-away selection left it off screen (Open Quickly, Jump to Column).
• An arrow pressed before a new query's results land is replayed on those results, in order. It moved in the old list and was then reset.
• The two filter functions are @concurrent. Under approachable concurrency they ran on the main actor: 100 to 400 ms per keystroke in the Connections scope with 5 to 10 connections of 2,000 tables.
• Completion list: a click selects at once instead of after the double-click interval (about 350 ms), and the list scrolls only as far as the row needs, so a double click stays on its row.

	Light	Dark
Before
After

Test plan

• QuickSwitcherSelectionRenderingTests renders the real panel and reads the drawn selection: highlight after a query, scroll back to a kept selection, header on arrow up. All three fail on main.
• QuickSwitcherViewModelTests: rows, arrows replayed in order with clamping, a keystroke drops a pending arrow, same-search refilter, search generation. ColumnJumpViewModelTests: search generation.
• verify: build, test (Quick Switcher, Jump to Column, recent tabs, completion suites), lint, l10n. OpenQuicklyCommandUITests runs on CI only, since Automation Mode is off on this Mac.

Fixes #3785