Rewrite tab/window subsystem: TabSession source of truth, fix rapid Cmd+Number animation queue

[datlechin]

Summary

• Rewrite the editor tab/window subsystem so per-tab state lives in a single TabSession (@Observable @MainActor class) instead of being scattered across 13 stores. The MainContentCoordinator god-object shrinks substantially; query execution is extracted into a focused QueryExecutor service; lifecycle work moves to Apple-documented hooks.
• Fix the rapid-Cmd+Number tail-of-switching bug: selectTab(number:) now uses NSWindowTabGroup.selectedWindow wrapped in NSAnimationContext.runAnimationGroup(duration: 0) so AppKit doesn't queue a CAAnimation per press. windowDidBecomeKey is now the lightweight Apple-documented contract — lazy-load runs through SwiftUI's .task(id:) view-appearance lifecycle instead.
• Net diff: +2794 / -1609 across 71 files (production net is much smaller — most insertions are tests + the architecture doc).

What landed (per phase)

The refactor was done as a strangler-fig migration tracked across 5 logical phases. See docs/architecture/tab-subsystem-rewrite.md for the full design doc with Apple-source citations and the migration plan.

Phase	Delivered	Removed
PR1	TabSession.swift (foundation type), design doc, tests	—
PR2	TabSessionRegistry (UUID→TabSession bridge), loadEpoch field on QueryTab + TabSession, TableRowsStore becomes facade	—
PR3	QueryExecutor.swift, QuerySqlParser.swift, 22 tests	432-line query path inside MainContentCoordinator decomposed
PR4	selectTab(number:) uses NSWindowTabGroup.selectedWindow + NSAnimationContext; lazyLoadCurrentTabIfNeeded on coordinator; .task(id: TabLoadKey) on MainEditorContentView; deferred eviction sort	onWindowBecameKey/onTeardown/onWindowWillClose stored closures, lastResignKeyDate field, 200ms isMenuBounce guard
PR5a	row-access API on TabSessionRegistry	TableRowsStore.swift (75 lines)
PR5b	ColumnVisibilityPersistence.swift, MainContentCoordinator+ColumnVisibility.swift rewritten	Models/UI/ColumnVisibilityManager.swift (83 lines)
PR5c	MainContentCoordinator+FilterState.swift (per-tab helpers), TabFilterState now single-source-of-truth on QueryTab.filterState mirrored to TabSession	FilterStateManager class (350 lines) — kept FilterLogicMode enum + TabFilterState ext
PR5d	—	MainContentCoordinator+MongoDB.swift (empty)
PR5e	CHANGELOG audit, design doc completion notes	—

Cmd+Number lag bug

The user-visible "switching continues after key release" symptom is fixed in PR4 by the NSAnimationContext.runAnimationGroup(duration: 0) wrapping (Apple-documented anti-animation idiom — not a custom debouncer/coalescer). Per-switch AppKit overhead remains because TablePro intentionally uses one NSWindow per tab (.tabbingMode = .preferred) for native integration; this is an accepted platform trade-off documented in docs/architecture/tab-subsystem-rewrite.md D2.

State migration: before → after

State	Before	After
Filters	FilterStateManager (3 copies: live, snapshot, UserDefaults)	QueryTab.filterState mirrored to TabSession.filterState; FilterStatePersistence enum for UserDefaults
Hidden columns	ColumnVisibilityManager global, swap on tab switch	QueryTab.columnLayout.hiddenColumns mirrored to TabSession.columnLayout; ColumnVisibilityPersistence enum for UserDefaults
Row data	TableRowsStore[id] keyed by tab UUID	TabSession.tableRows, accessed via TabSessionRegistry
Load-epoch	(didn't exist)	TabSession.loadEpoch (bumped on eviction; drives .task(id:) re-fire)
Stored closures	onWindowBecameKey, onTeardown, onWindowWillClose	gone — direct strong refs + syncSidebarToSelectedTab method

Out of scope (future work)

• ConnectionToolbarState per-tab semantics — currently per-connection, migrating to per-tab would change UX (toolbar state would differ between tabs in same window). UX decision needed first.
• Splitting MainContentCoordinator into a separate TabGroupCoordinator per the original design doc target — coordinator's responsibilities are now scoped properly via the per-domain helpers; deeper split deferred.

Test plan

• Build cleanly in Xcode (no compile errors).
• Run the test suite — existing tests pass; new tests cover TabSession round-trip, TabSessionRegistry, QueryExecutor SQL parsing/parameter handling, ColumnVisibilityPersistence, FilterStatePersistence, lazyLoadCurrentTabIfNeeded guard contract.
• Manual: open a connection, open multiple tables (multiple native window tabs).
• Manual: rapid Cmd+Number burst — confirm no tail of animations after key release.
• Manual: switch tabs (Cmd+Shift+]), confirm filter state preserved per-tab.
• Manual: hide columns on one tab, switch, confirm hidden state preserved per-tab and persisted across sessions.
• Manual: close a window with unsaved changes — confirm aggregated save invariant preserved (sibling windows not clobbered).

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Exclude selected tab from deferred eviction candidates

handleTabChange now defers eviction with Task { ... }, so rapid tab switches can queue eviction jobs that run after selection has changed; this candidate guard only checks the captured activeTabIds and does not exclude the current selectedTabId, so a stale task can evict the tab the user is actively viewing and clear its rows unexpectedly. Add a guard against tab.id == tabManager.selectedTabId inside the eviction filter (or cancel/coalesce prior eviction tasks) to prevent active-tab data loss during fast navigation.

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[chatgpt-codex-connector]

Drive TabLoadKey from the epoch that eviction actually updates

The lazy-load task key uses tabManager.selectedTab?.loadEpoch, but eviction increments TabSession.loadEpoch in TabSessionRegistry and never propagates that change back to QueryTab.loadEpoch; as a result, the epoch portion of this task ID never changes after eviction, so .task(id:) will not re-fire when rows are evicted without a tab-ID change. This breaks the intended eviction-triggered reload path and can leave an evicted tab blank until a manual refresh.

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