Sidebar: extract 7 hooks and 7 components into src/components/sidebar/ (#1447 pass T) - #1471

Round 6, pass T of #1447. This extracts 7 hooks and 7 stateless components from the Sidebar component body into src/components/sidebar/, one commit each. The state map, plan and reasoning are in docs/superpowers/specs/2026-10-05-sidebar-split.md.

Hooks: useSidebarRows (140 lines), useSidebarShortcuts (104), useThreadSearch (71), useListAnimation (58), useProviderOptions (40), useMoreMenuFocus (36), useStableThreadTitles (27).

Components: FilterBar (484), CreateThreadMenu (271), TrashedShelf (123), ScopeMenu (119), RemoveProjectConfirm (118), InsightsMenu (117), BatchBar (82).

Sidebar.tsx: 3,328 → 2,124 lines.

Checked

• Effect order: a script lists the component's effects on main, then on this branch with each hook expanded at its call site. Both have the same 14 effects, with the same kind and opening line, in the same order.
• New components hold no state or refs; they render from props.
  • RemoveProjectConfirm keeps main's removeConfirmId && guard. The old inline projectById lookup / null return now sits inside the component.
  • removeConfirmRef is passed through and attached to the dialog, so useModalFocus / useEscapeClose in the parent still work.
• Pure move, ignoring indentation: the only non-move lines are hook calls and returns, JSX props, and that guard.
• Screenshots against main (default, search, filter bar, scope menu, Insights menu, folded rail): three are byte-identical and three differ by YMAX 1, an invisible anti-aliasing difference.
• npm run typecheck and npx vite build are clean. Renderer suite: 2701/2701, 0 cancelled (TAP count).

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