rework session layer on PasswordSession + three-client pattern

- PasswordSession (@atproto/lex-password-session) is now the single auth
  core; SessionAgent bridges it to the base Agent from @atproto/api so
  the ~148 useAgent() consumer files keep working unchanged
- SessionBundle carries {session, agent, accountClient, appviewClient};
  useLexClient() now returns the authed appview client, new
  useAppviewClient()/usePdsClient() hooks
- reducer: OpaqueSessionBundle, new replaced-current-bundle action for
  network-free cross-tab same-did sync (PasswordSession is immutable, so
  the bundle is rebuilt instead of mutated in place)
- moderation: AtpAgent.configure -> Client.configure + Agent.configure,
  per-account labelers on both the bridge and the appview client
- push-token unregistration uses temporary PasswordSessions
- hard-tail migrations: SignupQueued refresh via resumeSession shim,
  useBeginAgeAssurance scoped-token raw Client, useAccountEmailState
  reads currentAccount
- PDS routing preserved on the no-network resume fast path by
  synthesizing a minimal didDoc from the persisted pdsUrl

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/screens/SignupQueued.tsx

@@ -41,7 +41,7 @@ export function SignupQueued() {
       const res = await agent.com.atproto.temp.checkSignupQueue()
       if (res.data.activated) {
         // ready to go, exchange the access token for a usable one and kick off onboarding
-        await agent.sessionManager.refreshSession()
+        await agent.resumeSession()
         if (!isSignupQueued(agent.session?.accessJwt)) {
           onboardingDispatch({type: 'start'})
         }