fix(tabs): single-click reuses the active tab window-locally (#1348)

[datlechin]

Fixes #1348.

Problem

The first table click replaced the current tab, but once a second tab existed, every later click opened a new tab instead of replacing the active one.

Root cause

The replace-vs-new-tab decision was made outside the focused window. openPreviewTab scanned every window of the connection for a preview flag and replaced whichever window held it, stealing focus to a different window. That window-level preview flag was a second source of truth that drifted out of sync with QueryTab.isPreview. With preview tabs off there was no reuse path at all, so every click spawned a tab.

Fix

Single-click is now window-local, with QueryTab.isPreview as the only source of truth:

• Reuse the focused window's active tab when it is reusable (a preview tab or a blank query tab) and has no unsaved work.
• Otherwise open a new tab and leave the current one alone.
• enablePreviewTabs only decides whether the resulting tab is a preview.

This matches the macOS convention (single-click opens in place, double-click opens) and the Xcode/VS Code one-temporary-tab model. Pinned and working tabs are protected; double-click opens a table in its own permanent tab.

Removed the cross-window preview lookup (WindowLifecycleMonitor.previewWindow/setPreview/Entry.isPreview) and deleted openPreviewTab.

Tests

• Rewrote SidebarNavigationResultTests for the new .skip / .reuseActiveTab / .openNewTab contract.
• Added coordinator tests in OpenTableTabTests: window-local reuse (preview on, and a blank query tab), pinned-tab protection, promotion, and double-click opening a permanent tab.

swiftlint --strict clean.