[SDK] Validate and brand the persisted account did (#11387)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/state/persisted/schema.ts

@@ -1,3 +1,4 @@
+import {isDidString} from '@atproto/lex'
 import {z} from 'zod'
 
 import {deviceLanguageCodes, deviceLocales} from '#/locale/deviceLocales'
@@ -13,7 +14,17 @@ const externalEmbedOptions = ['show', 'hide'] as const
  */
 const accountSchema = z.object({
   service: z.string(),
-  did: z.string(),
+  /**
+   * Genuinely validated, not just branded: the refinement rejects malformed
+   * values at runtime and narrows the inferred type to `DidString`.
+   *
+   * Weigh any further tightening of this field carefully. One failing field
+   * fails the whole root schema, and {@link tryParse} then discards the ENTIRE
+   * persisted state - every account and every preference - so the app boots
+   * logged out with defaults. Persisted dids come from com.atproto.server
+   * responses and are always canonical, so this particular check is safe.
+   */
+  did: z.string().refine(isDidString),
   handle: z.string(),
   email: z.string().optional(),
   emailConfirmed: z.boolean().optional(),