Add apps/core, a Kotlin Multiplatform client core shared by Android,
macOS, and iOS: identity, routing, connection supervision, sync and the
replica store, the durable outbox, boards, navigation, drafts and task
capture, conversations and their presentation, schedules, terminals,
workspace and git, files, admin, quotas, activity and notifications,
search, executions, and screens. It ships the DieterShared framework for
Apple and is tested on the JVM, natively on macOS, from Swift, and as
the Android variant against isolated gateways and daemons.

Android now runs entirely on the core. Its logic layer, protobuf-lite,
and grpc-java are gone, and the app keeps only Compose presentation and
Android adapters (OkHttp transport, Keystore credentials, WebRTC and
MediaCodec screen media, notifications, widgets, the updater, and the
background service). Presentation rules also live in the core, so every
client words and decides things the same way.

Fixes found on the way:
- Settings and shared-record conflicts are read and written on the same
  project replica instead of saving to whichever machine is attached.
- Creating a file inside a folder no longer doubles the folder path.
- A closed file no longer reopens on the next listing, and a save
  conflict keeps the draft dirty with a Reload action.
- Tasks for an offline destination queue against the cached catalog.

CI gains kmp and kmp-apple jobs; check-changed routes core changes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>