Keep the Tauri boot splash until the server is up, and get there faster

[joepio]

Related Issues

The desktop and Android apps open the webview before the embedded atomic-server binds. The HTML splash disappeared as soon as React started, the Store fetched into a dead port, and the page settled on "Could not reach the server" — for a node that was about to answer in milliseconds. On a failed start (another atomic-server holding the data directory) the splash also spun forever with no reason.

First contentful paint of the real app was then delayed further: HTTP bind waited on the Iroh n0 relay (up to 10s on a slow or offline network), React wiped the splash for IdentityReconcileGate's empty first paint, and the Tauri shell preloaded ~6MB of unused OPFS WASM.

Checklist

• Add changelog entry linking to issue, describe API changes
• Add or update tests if needed
• Update docs if needed

What changed

The existing boot splash (spinning AtomicServer lockup in index.html) now stays up until the embedded node is actually accepting connections. The Store is not created until then, so the first fetch cannot race the bind.

Readiness is node_status, a new Tauri command: our store is up and the HTTP port is accepting (the embedder hook fires before bind(), so the store alone is too early). A startup error — the usual "Database already open" case — is written onto the splash instead of spinning forever.

HTTP HEAD is the fallback when invoke is missing, so e2e tests that fake __TAURI_INTERNALS__ without a real shell still resolve against the already-running test server. When IPC answers {ready:false}, we do not also download the SPA.

To get real content on screen sooner:

• Iroh's n0 relay wait (up to 10s) no longer blocks HTTP bind. Same-LAN mDNS does not use the relay; WAN discovery still completes in the background.
• The splash lives outside #root (#boot-splash) so React mount and IdentityReconcileGate cannot blank it. The gate fades it once children are about to paint.
• The Tauri HTML transform drops unused WASM preloads (~6MB) and the atomicdata.dev preconnect. Fonts load asynchronously in the Tauri build.

Tests

• waitForEmbeddedServer.test.ts: no-op in a browser, ready via node_status, HTTP HEAD fallback, skip HTTP when IPC already answered, fail-fast on startup error, retries, timeout, splash error DOM, hideBootSplash.
• tauriHtml.test.ts: the Tauri transform strips WASM/atomicdata preloads from index.html.
• tauri.test.ts still covers origin detection.

Test Files  3 passed (3)
Tests  19 passed (19)

cargo check -p atomic_lib --features db-redb,iroh --lib and cargo check -p atomic-server --lib succeeded. cargo check -p atomic-server-tauri could not run in this environment (no gdk-3.0). The Tauri GUI cannot be launched here; JS unit tests cover the splash/readiness path.

Notes

Pairing over Iroh is unchanged: POST /iroh-sync already polls until a node id is advertised, because HTTP being up never meant the transport was dialable.