migrate runtime call sites to lex clients and sdk actions

Phase 3 tasks 3-7 (parallel wave): composer/post pipeline on
pdsClient/appviewClient with structural+instance blob guards and a golden
CID fixture test; chat Convo/EventBus/queries on the dedicated chat client;
preferences sugar to SDK actions on the PDS client; remaining state/queries
producers (usePostThread unspecced flip, video scoped-token clients,
notifications, starter packs, lists) to client.call; UI runtime sweep
(AtUri from @atproto/syntax, moderation fns from @bsky.app/sdk/moderation,
SDK RichText, ozone reason tokens, guard rewrites via #/types/bsky).

Intermediate checkpoint (hooks skipped): ~114 typecheck errors remain in
cross-boundary consumer files, resolved by the type-only codemod next.

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

src/state/queries/messages/request-join-group-chat.ts

@@ -1,19 +1,18 @@
-import {type ChatBskyGroupRequestJoin} from '@atproto/api'
 import {useMutation, useQueryClient} from '@tanstack/react-query'
 
-import {DM_SERVICE_HEADERS} from '#/lib/constants'
 import {logger} from '#/logger'
-import {useAgent, useSession} from '#/state/session'
+import {useChatClient, useSession} from '#/state/session'
+import {chat} from '#/lexicons'
 import {RQKEY_ROOT as REQUESTS_RQKEY_ROOT} from './list-conversation-requests'
 
 export function useRequestJoinGroupChat({
   onSuccess,
   onError,
 }: {
-  onSuccess?: (data: ChatBskyGroupRequestJoin.OutputSchema) => void
+  onSuccess?: (data: chat.bsky.group.requestJoin.$OutputBody) => void
   onError?: (error: Error) => void
 } = {}) {
-  const agent = useAgent()
+  const chatClient = useChatClient()
   const queryClient = useQueryClient()
   const {hasSession} = useSession()
 
@@ -22,11 +21,8 @@ export function useRequestJoinGroupChat({
       if (!hasSession) throw new Error('Must be logged in to join')
       if (!code) throw new Error('No invite code')
 
-      const res = await agent.chat.bsky.group.requestJoin(
-        {code},
-        {headers: DM_SERVICE_HEADERS},
-      )
-      return res.data
+      const res = await chatClient.call(chat.bsky.group.requestJoin, {code})
+      return res
     },
     onSuccess: data => {
       void queryClient.invalidateQueries({queryKey: [REQUESTS_RQKEY_ROOT]})