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/link-meta/link-meta.ts

@@ -1,8 +1,9 @@
-import {type AppBskyEmbedExternal, type AtpAgent} from '@atproto/api'
+import {type AppBskyEmbedExternal} from '@atproto/api'
 
 import {LINK_META_PROXY} from '#/lib/constants'
 import {getGiphyMetaUri} from '#/lib/strings/embed-player'
 import {parseStarterPackUri} from '#/lib/strings/starter-pack'
+import {type SessionAgent} from '#/state/session'
 import {isBskyAppUrl} from '../strings/url-helpers'
 
 export enum LikelyType {
@@ -31,7 +32,7 @@ export interface LinkMeta {
 }
 
 export async function getLinkMeta(
-  agent: AtpAgent,
+  agent: SessionAgent,
   url: string,
   timeout = 15e3,
 ): Promise<LinkMeta> {