feat: browser-native client — wire SPA to the SDK, delete the Go gateway

Phase 2 of issue 0001. uniweb becomes a pure frontend (web/ only), like
unibus_android: the SPA talks directly to the bus and the Go gateway is gone.

- busService.ts: the new data layer over the bus SDK, replacing the old api module.
  It holds the user's wallet identity and a connected BusClient IN THE BROWSER and
  opens the session locally — the private key is never sent anywhere (closes the
  gateway-era hole where the browser POSTed its private key to /api/session).
- Wire account/App/ChatShell/ChatPanel/WalletLogin/Recover/Join to busService;
  subscribeRoom replaces the SSE streamRoom; ApiError -> SessionError.
- SDK: ControlPlane.createRoom + listMemberRooms, and fetchRoom mapped to the real
  control-plane wire shape (snake_case, no id) — all verified by the live round-trip.
- Delete cmd/webgw, go.mod, go.sum, src/api.ts and the orphan operator Login. uniweb
  now has zero Go and no dependency on unibus as a module.
- vite: drop the /api proxy, dev server on 5173 to match the bus CORS allowlist; add
  vite-env typings. app.md: lang ts, no uses_functions, e2e_checks are now web-only.
  Bump 0.3.0.

Onboarding by token is now admin-side (the bus has no self-register endpoint; the
gateway only mocked it). tsc + pnpm build + 19/19 unit green.

web/src/wallet/account.ts

@@ -1,22 +1,19 @@
 // High-level wallet account operations shared by the join, recover and login
-// flows. These compose the low-level primitives (derive / crypto / store) with
-// the gateway API so the page components stay thin.
+// flows. These compose the low-level primitives (derive / crypto / store) with the
+// browser-native bus session so the page components stay thin.
 
-import { api } from "../api";
-import type { MeInfo, User } from "../types";
+import { bus } from "../busService";
+import type { User } from "../types";
 import { decryptJSON, encryptJSON } from "./crypto";
 import type { WalletIdentity } from "./derive";
 import { getIdentity, putIdentity, type StoredIdentity } from "./store";
 
-function toUser(me: MeInfo): User {
-  return { id: me.endpoint, handle: me.handle || me.endpoint.slice(0, 8) };
-}
-
-// saveAndOpen encrypts the identity under `password`, stores it on this device,
-// and opens a gateway session as that user. Used by join (new identity) and
-// recover (re-derived identity): both end with a locally-encrypted key plus a
-// live per-user session. The mnemonic/seed is NOT touched here — only the derived
-// keypair is persisted (encrypted).
+// saveAndOpen encrypts the identity under `password`, stores it on this device, and
+// opens a bus session as that user. Used by join (new identity) and recover
+// (re-derived identity): both end with a locally-encrypted key plus a live session.
+// The mnemonic/seed is NOT touched here — only the derived keypair is persisted
+// (encrypted). The private key is used to open the session IN THE BROWSER and is
+// never sent to any server (unlike the old gateway model).
 export async function saveAndOpen(
   identity: WalletIdentity,
   handle: string,
@@ -30,19 +27,17 @@ export async function saveAndOpen(
     enc,
     createdAt: Date.now(),
   });
-  const me = await api.session(identity, handle);
-  return toUser(me);
+  return bus.openSession(identity, handle);
 }
 
 // unlockAndOpen reads this device's stored identity, decrypts the private key with
-// `password`, and opens a gateway session. Throws WrongPasswordError on a bad
+// `password`, and opens a bus session locally. Throws WrongPasswordError on a bad
 // password (GCM auth failure) and NoLocalIdentityError if the device has none.
 export async function unlockAndOpen(password: string): Promise<User> {
   const stored = await getIdentity();
   if (!stored) throw new NoLocalIdentityError();
   const identity = await decryptJSON<WalletIdentity>(stored.enc, password);
-  const me = await api.session(identity, stored.handle);
-  return toUser(me);
+  return bus.openSession(identity, stored.handle);
 }
 
 // localIdentity returns the device's stored identity record (or null), for the