Move to @pezkuwi/dev 0.86.4 (eslint 10 toolchain)

- dev ^0.86.4 at the root and in packages/apps; directives renamed by
  pezkuwi-dev-migrate-eslint10.
- eslint --fix with the 0.86.4 config; one fix broke syntax
  (typescript-eslint prefer-optional-chain turned
  `(isStarted && onStart) && onStart()` into `(isStarted && onStart?.();`
  in TxButton) and is corrected by hand.
- The remaining findings fixed rather than disabled: optional chains
  (each suggestion reviewed), `cause` on rethrown errors, `if` instead of
  `a && promise` in effects, parallel instead of sequential awaits in
  Promise.all, Error rejections, no `delete` on arrays (the storage query
  cache is a Map; an upload's file list no longer keeps a hole), no
  `[object Object]` stringification (TFunction's second argument is text
  or options), dead code removed (referenda's never-shown expand button,
  react-query's unused CoreDescriptor).

packages/page-staking/src/Validators/Address/StakeOther.tsx

@@ -70,7 +70,7 @@ function StakeOther ({ nominators, stakeOther }: Props): React.ReactElement<Prop
 
   return (
     <td className='expand all'>
-      {(!rewarded || rewarded[0] !== 0) && (
+      {(rewarded?.[0] !== 0) && (
         <ExpanderScroll
           className={rewarded ? '' : '--tmp'}
           renderChildren={rewarded?.[1]}