[f-liva]

Summary

On a web tab left open for hours with dozens of streaming sessions, every socket event re-rendered every mounted row of the sessions list; an overnight heap reached 1.2 GB. Three per-row costs in sources/components/SessionsList.tsx and sources/components/FlatSessionRow.tsx add up to that: FlatSessionRow and SessionItem are React.memo'd, but every list rebuild hands them a freshly minted SessionRowData, so the default identity comparison failed for every row in the visible window on every event. Every row also mounted a SessionActionsPopover with visible={false}, which ran useSession, useSessionQuickActions, useWindowDimensions and the safe-area hook before returning null — a dozen store subscriptions and memos per row, all woken by every session update. And on web every row called useSessionActionAlert (sources/hooks/useSessionQuickActions.ts), paying a useSession subscription plus the whole quick-actions hook for an onLongPress handler that only native ever invokes.

This PR gives the two row memos a comparator that deep-equals the row data (flat primitives, so fast-deep-equal is cheap) together with the primitive props, mounts the popover only while the row holds an anchor (closing clears the anchor and unmounts it, as before), and picks a no-op useSessionActionAlert once at module load on web — Platform.OS is constant, so hook order stays stable and the native variant is unchanged.

Changes

• FlatSessionRow / SessionItem: add memo comparators that compare selected/isFirst/isLast/isSingle and deep-equal the row data instead of relying on object identity
• Mount SessionActionsPopover only while actionsAnchor is set, on both the flat and the grouped row
• useSessionActionAlert: export a no-op variant on web, keep the native one as is

Test plan

• pnpm typecheck (clean)
• pnpm exec vitest run sources/components/HomeHeader.test.ts sources/components/sessionPresentation.test.ts sources/utils/flatSessionList.test.ts sources/utils/flatSessionRowPresentation.test.ts (the specs that cover the row presentation and list shape; all pass — the change is render-count only, no behavioural test exists for it)
• Ran on a self-hosted web deployment: sessions list still updates thinking/unread/order; row actions popover (hover button and right-click) opens, closes and unmounts; command palette works

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