Frontend: move the start sequence into an exported bootstrap() for embedding apps #882

Goal

The frontend start sequence lives in one exported function bootstrap(). An embedding app with its own frontend entry point calls it instead of copying main.tsx, so every future start step (platform attribute, context-menu suppression, startup state, language, startup gate, root error boundary) reaches it automatically.

Context

• apps/smart-ssh-community/frontend/src/main.tsx holds the whole start sequence as top-level code:
  • :13 document.documentElement.dataset.platform = detectFallbackPlatform() (Spec 0114, narrow Android layout)
  • :33-38 getStartupState() before the first render (Spec 0101, A16)
  • :48-50 initI18n(...) with the language from the startup state
  • :53 installContextMenuSuppression() in production builds (Suppress the WebView context menu ("Reload") in release builds; add "Refresh" to the file browser's empty-space menu #629)
  • :56-62 createRoot(...).render(<StrictMode><StartupGate initialState=…><App/></StartupGate></StrictMode>)
  • after Frontend: isolate every extension contribution and the app root with an error boundary #880: the root ErrorBoundary with the recovery screen.
• An app that embeds this frontend and registers its own extension contributions has to repeat these steps; steps added later (like :13 and :53) are easy to miss there.
• Extensions that need React lifecycle (react to a state change, register and unregister a contribution) today have to wrap <App/> in their own components, one nesting level each.

Requirements

• New src/bootstrap.tsx exporting:

  export interface BootstrapOptions {
    /** Runs after initI18n and before the first render; may be async. */
    beforeRender?: () => void | Promise<void>;
    /** Headless components rendered once as siblings of <App/> inside the
     *  StartupGate (so only after unlock), each in its own ErrorBoundary. */
    extensions?: ReadonlyArray<{ id: string; Component: ComponentType }>;
    /** Optional wrapper around <App/> inside the StartupGate. */
    wrap?: (app: ReactNode) => ReactNode;
  }
  export async function bootstrap(options?: BootstrapOptions): Promise<void>;

  It performs exactly the steps of today's main.tsx, in the same order, then beforeRender, then renders. The root element id stays root.
• main.tsx imports ./index.css and calls await bootstrap() – nothing else.
• A failing beforeRender (throws/rejects) is logged with console.error and the app still renders (fail-open only for this optional hook; startup state and gate behaviour unchanged).
• Each entry of extensions is wrapped in ErrorBoundary (from Frontend: isolate every extension contribution and the app root with an error boundary #880) keyed by its id; a throwing extension does not affect <App/>.
• Spec 0038 section 4 (frontend extension points) describes bootstrap() and its options as the supported entry point for embedding apps.

Acceptance Criteria

• bootstrap() exists with the options above; main.tsx contains only the CSS import and the bootstrap() call.
• Tests (vitest, with getStartupState/initI18n mocked):
  • bootstrap() sets document.documentElement.dataset.platform.
  • In a production build flag (import.meta.env.PROD stubbed true) it installs the context-menu suppression; with PROD false it does not.
  • Order: getStartupState → initI18n (with the startup-state language when locked) → beforeRender → render.
  • A rejecting beforeRender is logged and the app still renders.
  • An extensions entry renders inside the gate only in the unlocked state; a throwing entry leaves <App/> rendered.
  • wrap receives the <App/> element and its result is rendered inside the gate.
• Existing startup tests (password mode, locked start, language before first render) and the Playwright suite pass unchanged.
• Spec 0038 section 4 updated.
• Relevant automated tests pass (npm run lint, npm test, tsc -b, npm run test:e2e).

Technical Notes

• Files: src/bootstrap.tsx (new), src/main.tsx, a new src/bootstrap.test.tsx, docs/specs/0038-repository-app-shell-ci.md.
• Keep the long comments from main.tsx (why the startup state comes first, Spec 0101 A16; why the language is set before the first render, Spec 0024) next to the code they explain in bootstrap.tsx; new comments in English.
• Top-level await moves into the async function; main.tsx keeps one top-level await bootstrap().
• StartupGate keeps sole control over when <App/> mounts; extensions are rendered inside it so they never call data commands while the app is locked (Spec 0101 A16).

Spec impact: update 0038

Open questions

• none

Related Work

• Frontend: isolate every extension contribution and the app root with an error boundary #880 (ErrorBoundary; blocks this issue)
• Suppress the WebView context menu ("Reload") in release builds; add "Refresh" to the file browser's empty-space menu #629, Spec 0114, Spec 0101