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/lib/api/feed/home.ts

@@ -1,6 +1,7 @@
-import {type AppBskyFeedDefs, type AtpAgent} from '@atproto/api'
+import {type AppBskyFeedDefs} from '@atproto/api'
 
 import {PROD_DEFAULT_FEED} from '#/lib/constants'
+import {type SessionAgent} from '#/state/session'
 import {CustomFeedAPI} from './custom'
 import {FollowingFeedAPI} from './following'
 import {type FeedAPI, type FeedAPIResponse} from './types'
@@ -27,7 +28,7 @@ export const FALLBACK_MARKER_POST: AppBskyFeedDefs.FeedViewPost = {
 }
 
 export class HomeFeedAPI implements FeedAPI {
-  agent: AtpAgent
+  agent: SessionAgent
   following: FollowingFeedAPI
   discover: CustomFeedAPI
   usingDiscover = false
@@ -39,7 +40,7 @@ export class HomeFeedAPI implements FeedAPI {
     agent,
   }: {
     userInterests?: string
-    agent: AtpAgent
+    agent: SessionAgent
   }) {
     this.agent = agent
     this.following = new FollowingFeedAPI({agent})