Plan 1b: Tauri mobile scaffolding + adaptive layout

[careck]

Parent: #171 (Mobile support: iOS and Android via Tauri v2)

Depends on: Device ID migration (#172)

Summary

Scaffold Tauri iOS and Android targets from the existing krillnotes-desktop package and implement adaptive layout with three breakpoints: phone (stack navigation), tablet portrait (compact sidebar), and tablet landscape/desktop (full side-by-side).

Plan

See docs/superpowers/plans/2026-04-29-mobile-scaffolding-layout.md on the mobile branch.

Key Changes

Tauri Scaffolding

• tauri ios init + tauri android init — generate platform projects
• #[cfg(desktop)] guards on native menu, close_window, multi-window logic
• Mobile capabilities file

Adaptive Layout

• useLayout() hook — returns "phone" | "tablet" | "desktop" based on viewport width
• MobileNav.tsx — stack navigator for phone: full-screen tree ↔ full-screen note with slide transitions
• BottomNavBar.tsx — phone bottom bar: Tree, Search, Tags (bottom sheet), More
• TagCloudSheet.tsx — slide-up bottom sheet for tag cloud on phone
• ToolbarMenu.tsx — hamburger menu (☰) replacing native menu on tablet/mobile
• WorkspaceView integration — layout-aware rendering, existing desktop unchanged

Touch UX

• Touch-enabled resizable panels (wider hit target, touch events)
• 44px minimum tap targets on tree nodes
• Long-press context menu (bottom sheet on phone, floating on tablet)
• Safe area padding (notch, dynamic island, home indicator)
• Swipe-back gesture on phone

i18n

• New keys across all 7 locale files for mobile UI elements

Target Devices

• Android phone (user's device)
• iPad (user's device)
• Desktop (regression testing)

Acceptance Criteria

• npm run tauri ios dev launches on iPad simulator
• npm run tauri android dev launches on Android device
• Phone layout: stack navigation works, bottom bar functional, tags sheet slides up
• Tablet portrait: compact sidebar with draggable divider, hamburger menu works
• Tablet landscape: full desktop-like layout with touch-friendly targets
• iPad rotation: layout transitions between tablet portrait ↔ landscape
• Desktop: zero regressions, native menu still works
• All 7 locale files updated with new keys