Extract current-document persistence actions from App.vue

[Renakoni]

Summary

Fourth PR of the semantic-decomposition series: moves every way the current editor document is persisted or exported out of App.vue into a createCurrentDocumentPersistence factory in features/document-session. Behavior-preserving; the save/share workflows and document-state transitions are reused unchanged, per the TODO.

Boundary

The factory owns:

• Local-draft autosave (saveDraft) with its target/setting guards and status transitions.
• Android document save (saveAndroidDocument) including the in-flight coalescing flags (a save requested during a save re-schedules once the first completes, preserving the changed-during-save path) and the read-only/missing-source/clean short-circuits.
• Draft-to-device save and save-a-copy flows with their cancel/transient/saved/failed branches, busy flags, and exit-prompt interplay.
• Sharing the current document with its busy guard.
• Lifecycle flush routing to the save path matching the current autosave target.
• Recovery-draft bookkeeping (persist with the setting guard, removal) and recents saved-marking — the latter stays private to the module since its only caller is the Android save path.

Everything App owns is injected: state refs (document state, status, notices, busy flags, prompt flags, stores), editor access (hasEditor, snapshot, sync), chrome closers, predicates and presentation helpers, store persistence + rememberAndroidDocument (shared with the open paths, so it stays in App), the autosave-scheduler timer handles, natives, settings refs, and loggers. App destructures the same function names — every call site (exit prompts, editor menu/actions sheet, incoming-document orchestration, lifecycle flush) is textually unchanged.

One wiring note: the autosave scheduler now receives saveDraft/saveAndroidDocument as deferred closures, because the two factories reference each other's handles (scheduler triggers saves; saves clear/reschedule timers) and const initialization order would otherwise TDZ.

App.vue shrinks by ~400 lines.

Testing

• New currentDocumentPersistence.test.ts (12 tests) drives the real save/share/copy workflows with mocked natives: draft autosave success + skip guards, Android save success updating recents and dropping the recovery draft, save failure keeping a recovery draft (and the users-message fallback when recovery drafts are disabled), in-flight coalescing with post-completion rescheduling, flush routing and its screen guard, draft-to-device saved/canceled-reopens-prompt paths, save-a-copy clearing the exit prompt and the original recovery draft, share success and the busy guard.
• Full unit suite 296/296, ESLint, vue-tsc, production build green.
• Contract E2E 28/28: mobile-local-draft-lifecycle (autosave + all four lifecycle flush paths), mobile-android-document-lifecycle (save-failure recovery, read-only exit flows), mobile-android-document-actions (save-copy variants, transient access), mobile-share-intent (current-document share paths).