Effort: Break up TabManager by concern, not by component

Notes: TabManager.tsx is ~1,560 lines on 7_0_0 (render 250, checkKey 249, selectTo 133, search 126, loadStorage 78); the same <Window> element is written twice for minimized/normal passes; the tab-walk loop in checkKey is pasted 4×. Keep it a class component and move logic into plain modules, each step independent, in this order: (1) popup/browserEvents.ts, subscribe({fast, slow, message, storage}) returning an unsubscribe, mount/unmount become two lines; (2) popup/duplicates.ts, getDuplicates(tabs) is already pure; (3) popup/search.ts, parseQuery / matchTab / searchTabs(tabs, query) returning the hidden ids, pure, fixes 1.16 by construction, first candidate for vitest (2.10); (4) popup/tabActions.ts, typed wrappers closeTabs / discardTabs / moveToWindow / openInNewWindow / focusTab around sendMessage<ICommand>, so deleteTabs / discardTabs / addWindow / pinTabs / drop / dropWindow shrink to selection + call; (5) settings, see 1.21; (6) popup/selection.ts, a Selection class over the Set with toggle, range (today selectTo), tabs(tabsbyid), clear, replacing the in-place mutation of state.selection (feeds 4.3); (7) popup/keyboard.ts, checkKey as a key → action table, the handler becomes a dispatch, the 4× tab-walk collapses, and the B4 cursor model lives here; (8) last, render split into Toolbar, HoverHeader, WindowList function components fed by props/context. Target: TabManager ≈ 400 lines (state, lifecycle, update(), the actions object, render composition). Not planned: hooks rewrite, a state library, or splitting the context into several providers; no gain at this size

Status (2026-10-10): Open. TabManager.tsx has grown to 2,867 lines. Steps 2, 3 and 5 exist (popup/duplicates.ts, popup/search.ts, helpers/settings.ts), along with small pure helpers such as arrowWalk.ts, selectionKeys.ts, openMovePlan.ts, dragPayload.ts, pendingDelete.ts. Steps 1, 4, 6, 7 and 8 do not exist (no browserEvents.ts, tabActions.ts, selection.ts or keyboard.ts)

Left as is ·