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/Onboarding/util.ts

@@ -2,7 +2,6 @@ import {
   type $Typed,
   type AppBskyGraphFollow,
   type AppBskyGraphGetFollows,
-  type AtpAgent,
   type ComAtprotoRepoApplyWrites,
   type ComAtprotoRepoStrongRef,
 } from '@atproto/api'
@@ -10,9 +9,10 @@ import {TID} from '@atproto/common-web'
 import chunk from 'lodash.chunk'
 
 import {until} from '#/lib/async/until'
+import {type SessionAgent} from '#/state/session'
 
 export async function bulkWriteFollows(
-  agent: AtpAgent,
+  agent: SessionAgent,
   dids: string[],
   via?: ComAtprotoRepoStrongRef.Main,
 ) {
@@ -59,7 +59,7 @@ export async function bulkWriteFollows(
 }
 
 async function whenFollowsIndexed(
-  agent: AtpAgent,
+  agent: SessionAgent,
   actor: string,
   fn: (res: AppBskyGraphGetFollows.Response) => boolean,
 ) {