App startup and bootstrap

The app starts in one fixed order: the entry loads the polyfills and then the router; the root layout installs the error net, holds the native splash and decides the direction before anything opens; the app root opens storage once, connects the error log and hydrates the stores synchronously, mounts the providers in dependency order and releases the splash once the first screen is real. Buffered writes flush from one root hook when the app leaves the foreground. Optional kits (crash reporting, analytics, notifications, ...) plug into typed slots from one registry, so the root files stay canonical when a kit is added. One zero-dependency checker proves it.

Rules that must hold