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/custom.ts

@@ -9,11 +9,12 @@ import {
   getAppLanguageAsContentLanguage,
   getContentLanguages,
 } from '#/state/preferences/languages'
+import {type SessionAgent} from '#/state/session'
 import {type FeedAPI, type FeedAPIResponse} from './types'
 import {createBskyTopicsHeader, isBlueskyOwnedFeed} from './utils'
 
 export class CustomFeedAPI implements FeedAPI {
-  agent: AtpAgent
+  agent: SessionAgent
   params: GetCustomFeed.QueryParams
   userInterests?: string
 
@@ -22,7 +23,7 @@ export class CustomFeedAPI implements FeedAPI {
     feedParams,
     userInterests,
   }: {
-    agent: AtpAgent
+    agent: SessionAgent
     feedParams: GetCustomFeed.QueryParams
     userInterests?: string
   }) {