feat(#76): add testTag identifiers to composable elements for UI test targeting (#98)
Adds testTag modifiers to key interactive elements across the core
composables, enabling Espresso/Compose UI tests to locate them:
Navigation.kt — 'nav_*' on bottom bar items, 'drawer_*' on drawer items
HermesScaffold — 'back_button', 'menu_button', 'refresh_button'
StateViews.kt — 'loading_state', 'loading_spinner', 'error_retry_button',
'empty_state_action'
ChatScreen.kt — 'chat_input', 'send_button', 'interrupt_button'
Co-authored-by: M57 <hy4ri@users.noreply.github.com>
