[kobaltgit]

Summary

Adapts the egui desktop UI for portrait mobile viewports and Android (NativeActivity / arm64-v8a):

• Bottom Navigation Bar (widgets/bottom_nav.rs): 48 pt touch-friendly 5-tab bar (Page, Graph, Planning, Threads, Search) replacing the desktop WorkspaceStrip on compact screens (width < 640.0 pt or Android).
• Single-Column Drawer Navigation: On compact viewports, the sidebar acts as a full-screen drawer. Selecting or creating a page automatically collapses the drawer. The Android system Back button navigates from document back to sidebar instead of exiting.
• Safe Area Insets: Top inset (28 pt) for camera punch hole & status bar; bottom inset (36 pt) for Android 3-button navigation.
• Titlebar & Overflow Menu (⋮): Replaces window caption buttons on mobile with a compact titlebar and 3-dots overflow menu containing folder sync (sync_folder), IMAP email sync (open_imap), appearance (appearance), command palette, integrations, FAQ, and locale toggle.
• Responsive Modals: All modals (onboarding, appearance, confirm_delete, faq, shortcuts) adapt dynamically to screen width (clamp(280.0, ...)), fixing the issue where the onboarding tour dialog (hardcoded 560 pt) was cut off horizontally on phones.
• Toolbar Collision Fixes:
  • In planning_view.rs: task statistics moved to header subtitle on compact screens, preventing text overlap with the 4 segment tabs.
  • In graph/mod.rs & threads_view.rs: compact toolbar buttons without overflowing hint labels.
• Android Runtime: Added panic hook logging to android_logger (logcat), and fallback for settings_dir() to vault::app_data_dir() when desktop env vars (APPDATA, HOME, XDG_CONFIG_HOME) are missing.
• CI: Enabled Android build trigger on feat/** branches in .github/workflows/android.yml.

Detailed maintainer documentation: docs/NATIVE_MOBILE_RESPONSIVE_UI.md.

Verification

• All 340 tests pass in strict single-threaded mode: cargo test --manifest-path native/Cargo.toml --lib -j 1.
• Headless mobile layout tests added in widgets/bottom_nav.rs and modals/onboarding.rs.
• APK build verified via GitHub Actions (Debug APK (arm64-v8a)) and tested on physical Android device.