[datlechin]

Summary

• No classic toolbar mode: glass weight is the system's, set in System Settings > Appearance > Liquid Glass and Reduce Transparency, and the macOS 27 SDK ignores UIDesignRequiresCompatibility. Every surface follows the HIG instead.
• Main toolbar: Save Changes moves to the end of the trailing run (Refresh, Actions, Safe Mode, Save), so AppKit draws it in a section of its own, as HIG Item groupings asks for Save. A customized toolbar keeps its order (scripts/probes/check-toolbar-autosave-reorder.sh).
• Sidebar Tables / Favorites: small with the tabs role on macOS 27, a flat track instead of a glass capsule.
• View switching in the main window area is one PaneTabBar: a centred tab row, regular with the tabs role on macOS 27, over content that runs edge to edge. Structure, Create Table, Create Table forms, User Type, Compare detail. No bordered tab view, which boxed and inset the grids.
• View switchers in a pane's own bar or the inspector share viewSwitcherStyle(), small with the tabs role on macOS 27: results view mode, Query Plan, Version History, JSON results, the cell viewers, the trailing pane header, the geometry field, Data File sheets, Users & Roles detail.
• Create Table: add and remove sit at the foot of the grid, and the validation message and Create Table in a bar below it.
• Data File sheets turn into a menu past six sheets instead of eight (HIG Tab views).
• Data File uses AppKit's inspector toggle, Integrations the system inspector glyph, and Compare & Sync defaults to Icon Only like the other windows.
• The diagram zoom pill uses glass on macOS 26 and later, like the other floating controls.
• iOS 26: toolbar glyphs drop their circle through the shared ToolbarSymbols, and the Structure section bar uses safeAreaBar.
• A tab switch in Structure and Create Table commits the open cell edit before the new tab is published, so an edit cannot land on another tab's rows when the incoming grid mounts first.
• Users & Roles: the scope outline selects the scopes the checklist still edits when Privileges is shown again, instead of coming back with no highlight.
• The AI walkthrough diff picker reads Split, Unified like the other two.
• Tests changed on purpose: QueryPlanResultUITests, DataFileWindowUITests and the showStructure helper. On macOS 27 XCUITest reports a tabs-role control as a tab group of Tab elements (read from the CI element tree), so segments go through a new switcherSegment(_:in:).

Before	After

Test plan

• New: BindingCommittingGridEditTests, PrivilegeScopeOutlineSelectionTests, ViewSwitcherStyleTests, SidebarScopeControlTests.tabsRoleOnMacOS27, ToolbarSymbolsTests sort cases.
• 32 unit suites over the changed types, 372 cases passing; iOS build plus DataBrowserViewModelTests and ConnectionListRowModelTests, 49 passing; lint and l10n clean.
• UI flows not run locally: Automation Mode needs authentication on this Mac and another TablePro was running. CI runs them.
• Captured on macOS 27.0.1 only; macOS 26 and 13 to 15 take the #available fallbacks, covered by tests, not on screen.

Fixes #3844