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/lib/api/upload-blob.ts

@@ -1,38 +1,62 @@
 import {copyAsync} from 'expo-file-system/legacy'
-import {type Agent, type ComAtprotoRepoUploadBlob} from '@atproto/api'
+import {type BlobRef} from '@atproto/lex'
+import {type Client, type EncodingString} from '@atproto/lex-client'
 
 import {safeDeleteAsync} from '#/lib/media/manip'
 
 /**
- * @param encoding Allows overriding the blob's type
+ * The blob-upload response body: `{blob}`. lex `Client.uploadBlob` returns the
+ * full XRPC response, so callers read `res.body.blob` (the parsed blob ref).
+ */
+type UploadBlobResult = {blob: BlobRef}
+
+/**
+ * @param encoding Allows overriding the blob's type. Passed as the lex upload
+ * option (NEVER a content-type header - lex-client throws if the encoding is
+ * set via headers).
  */
 export async function uploadBlob(
-  agent: Agent,
+  client: Client,
   input: string | Blob,
   encoding?: string,
-): Promise<ComAtprotoRepoUploadBlob.Response> {
+): Promise<UploadBlobResult> {
   if (typeof input === 'string' && input.startsWith('file:')) {
     const blob = await asBlob(input)
-    return agent.uploadBlob(blob, {encoding})
+    return uploadBlobResult(client, blob, encoding)
   }
 
   if (typeof input === 'string' && input.startsWith('/')) {
     const blob = await asBlob(`file://${input}`)
-    return agent.uploadBlob(blob, {encoding})
+    return uploadBlobResult(client, blob, encoding)
   }
 
   if (typeof input === 'string' && input.startsWith('data:')) {
     const blob = await fetch(input).then(r => r.blob())
-    return agent.uploadBlob(blob, {encoding})
+    return uploadBlobResult(client, blob, encoding)
   }
 
   if (input instanceof Blob) {
-    return agent.uploadBlob(input, {encoding})
+    return uploadBlobResult(client, input, encoding)
   }
 
   throw new TypeError(`Invalid uploadBlob input: ${typeof input}`)
 }
 
+async function uploadBlobResult(
+  client: Client,
+  blob: Blob,
+  encoding?: string,
+): Promise<UploadBlobResult> {
+  /*
+   * The lex encoding option is a branded mime string (`${string}/${string}`);
+   * callers pass a plain mime string, so assert the brand here.
+   */
+  const res = await client.uploadBlob(blob, {
+    encoding: encoding as EncodingString | undefined,
+  })
+  return {blob: res.body.blob}
+}
+
 async function asBlob(uri: string): Promise<Blob> {
   return withSafeFile(uri, async safeUri => {
     // Note