Phase 8 — Utilities, hooks, formatters

[jonmatum]

Phase 8 — Utilities, hooks, formatters

Cross-cutting helpers used internally by the shell and worth sharing.

Hooks

• cn() — classnames merger (clsx + tailwind-merge)
• useBreakpoint(), useMediaQuery()
• useDisclosure() — open / close / toggle primitive
• useLocalStorage(), useSessionStorage() — SSR-safe
• useCopyToClipboard()
• useDebouncedValue(), useDebouncedCallback()
• useControllableState() — Radix-style controlled/uncontrolled
• useHotkey() — keyboard shortcut helper
• useMounted(), useIsomorphicLayoutEffect()

Formatters (locale-aware)

• formatDate, formatRelativeTime
• formatNumber, formatCurrency, formatPercent
• formatFileSize, formatDuration
• truncate, pluralize

Acceptance

• Each hook / formatter has unit tests
• All formatters honor the active locale from I18nProvider
• Tree-shakeable — importing one helper does not pull the whole module

Part of the next-shell app shell extraction plan.