Extract editor-session lifecycle from App.vue

[Renakoni]

Summary

Final proactive decomposition PR: the Muya editor instance and its runtime lifecycle move out of App.vue into a dedicated editor-session boundary, createEditorSession in src/features/editor/editorSession.ts. App.vue drops from 1,659 to 1,457 lines and no longer owns any low-level editor machinery — it composes screens and coordinates workflows, reaching the editor only through session accessors.

Ownership boundary

Before: App.vue held the module-scope editor variable, the init token, the host-element ref, initEditor / openEditor / destroyEditor, Markdown snapshot + document-state sync, post-open focus release, and the input/selection diagnostic hooks — ~250 lines of editor internals interleaved with page composition.

After — owned by the session:

• the Muya instance, host element, and editorReady state
• initialization with stale-init token protection, including the failure path
• the destroy → (remount through home) → init cycle behind openEditor
• getEditorMarkdownSnapshot / syncDocumentFromEditor (and the shared normalizeEditorMarkdown)
• post-open focus release
• input/selection diagnostics install/teardown and describeEditorInputState
• cleanup on destroy (timers, diagnostics, native tap listener, suppression reset)

Intentionally still in App.vue: navigation and screen composition, syncMarkdown (status text + autosave scheduling policy), focus/blur status handlers, Android document open/save/share workflows, persistence orchestration, home actions, back-button/exit decisions, toolbar and link/image business actions, settings maintenance, notices.

Why this is a session boundary, not a second app controller

The session receives App policy as injected collaborators — syncMarkdown, focus/blur handlers, the selection-lifecycle functions, autosave timer handles, closeEditorToolbar — and never decides status wording, autosave timing, or navigation policy itself. This is the same factory-with-injected-options pattern as createEditorSelectionLifecycle, createAutosaveScheduler, and createCurrentDocumentPersistence; the mutual references between session, scheduler, and selection lifecycle use the deferred-closure convention already established in App.vue.

Behavior equivalence

Every moved function is verbatim except two documented equivalence rewrites:

• syncMarkdown now calls the extracted syncDocumentFromEditor(markDirty) — same editor guard, same normalization, same updateDocumentMarkdown call it previously inlined.
• The init-complete log reads documentState.value.stats.* directly; the App computeds it previously used resolve to exactly those fields.

Initialization ordering, suppression reasons (editor-init, editor-init-stale, editor-init-failed, editor-destroy), token-based race protection, remount semantics (screen flip through home with suppression update skipped), unmount cleanup, and all logging are unchanged. editorRuntime gains only an export on CreateMuyaEditorOptions so the session can type the injected factory. No UI, persistence, navigation, or Android bridge changes; third_party/muya untouched.

Testing

• New editorSession.test.ts (14 tests, happy-dom): open/ready wiring, missing host element, stale-init supersession (a superseded init resolving late must not replace the live editor), remount-through-home cycle, snapshot/sync incl. flush and single-newline normalization, destroy/teardown, suppression skip on remount destroy, repeated open/close cycles, init failure, diagnostics install/teardown + late enabling via the settings watcher path, focus release, input-state description.
• Full unit suite: 326/326 (54 files). ESLint clean. pnpm build (includes vue-tsc -b) clean.
• Mobile WebView e2e contract specs covering editor startup/shutdown/navigation: mobile-home-navigation, mobile-local-draft-lifecycle, mobile-android-document-lifecycle, mobile-markdown-editing — 23/23 passed.

Per the decomposition plan, this is the last size-driven extraction; further refactoring should be driven by product changes, bugs, or ownership conflicts.