…ure from dual-cache desync cp-7.70.1 (#27854)

## **Description**

Fix HIP-3 asset ID lookup failure (`"Asset ID not found for
xyz:BRENTOIL"`) that blocked trading on HIP-3 markets when navigating
via the old Perps tab layout.

**Root cause**: Dual-cache desync between `#cachedValidatedDexs` (string
DEX names) and `#cachedAllPerpDexs` (raw API objects for `perpDexIndex`
computation). The standalone preload path
(`#getStandaloneValidatedDexs`) populated one cache but not the other.
When `#buildAssetMapping` later ran, it found "xyz" in `dexsToMap` but
couldn't compute its `perpDexIndex` because `#cachedAllPerpDexs` was
null.

**Why old Perps tab vs new Homepage Sections**: Both layouts sit inside
`Wallet/index.tsx`, which calls `startMarketDataPreload()` on mount.
This fires standalone HTTP calls that populate `#cachedValidatedDexs`
but not `#cachedAllPerpDexs`.

- **New homepage sections**: `PerpsSectionWithProvider` mounts
immediately. Stream hooks fire `ensureReady()` before or concurrently
with the standalone preload. Since `#cachedValidatedDexs` is often still
null, `fetchValidatedDexsInternal` runs fresh and sets **both** caches
correctly.
- **Old tab layout**: The Perps tab doesn't mount until the user taps
it. By that time, `startMarketDataPreload()` has already completed →
`#cachedValidatedDexs` is populated by standalone. When the tab mounts →
`getValidatedDexs()` → **cache hit** → `fetchValidatedDexsInternal` is
never called → `#cachedAllPerpDexs` stays null → `buildAssetMapping`
can't find "xyz".

**Changes (1 file, 3 sites)**:

1. **Root cause fix**: `#getStandaloneValidatedDexs` now sets
`this.#cachedAllPerpDexs = allDexs` after a successful `perpDexs()`
call, keeping both caches in sync.
2. **Cache poisoning fix**: Removed `this.#cachedAllPerpDexs =
this.#cachedAllPerpDexs ?? [null]` from the catch block in
`#buildAssetMapping`.
3. **Cache poisoning fix**: Replaced persistent `if (!cache) { cache =
[null] }` with local `const allPerpDexs = cache ?? [null]` — consumers
read the cache, only the owner writes it.

## **Changelog**

CHANGELOG entry: Fixed a bug where closing positions on HIP-3 markets
(e.g., xyz:BRENTOIL) failed with "Asset ID not found" when navigating
via the Perps tab

## **Related issues**

Fixes: HIP-3 asset ID lookup failure on old Perps tab layout

## **Manual testing steps**

```gherkin
Feature: HIP-3 position management via Perps tab

  Scenario: user closes a HIP-3 position from the old Perps tab
    Given user has an open position on a HIP-3 market (e.g., xyz:BRENTOIL)
    And user is using the old tab layout (homepage redesign v1 disabled)

    When user navigates to the Perps tab
    And user taps close on the xyz:BRENTOIL position
    Then the position closes successfully without "Asset ID not found" error

  Scenario: user opens a HIP-3 position from the old Perps tab
    Given user is on the Perps tab (old layout)

    When user navigates to xyz:BRENTOIL market and places a market order
    Then the order executes successfully with correct asset ID routing
```

## **Screenshots/Recordings**

### **Before**

Metro logs show the desync:
```
getValidatedDexs CACHE HIT {"cachedAllNull": true, "dexs": [null, "xyz"]}
buildAssetMapping state  {"allPerpDexsLen": 1, "cachedAllNull": true}
Could not find perpDexIndex for DEX xyz
Asset ID not found for xyz:BRENTOIL
```

### **After**

Metro logs show both caches in sync:
```
buildAssetMapping state {"allPerpDexsLen": 8, "cachedAllNull": false, "dexsToMap": [null, "xyz"]}
Asset map state at order time {"assetExistsInMap": true, "hip3AssetsCount": 54, "totalAssetsInMap": 283}
Resolved DEX-specific asset ID {"assetId": 110049, "coin": "xyz:BRENTOIL"}
usePerpsClosePosition: Close result {"success": true, "orderId": "359617825254"}
```

## **Pre-merge author checklist**

- [x] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
Coding
Standards](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [x] I've completed the PR template to the best of my ability
- [x] I've included tests if applicable
- [x] I've documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [x] I've applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Touches HIP-3 market routing/asset-ID mapping in
`HyperLiquidProvider`, so a mistake could break trading on some perps
markets; scope is small and localized to cache population/fallback
behavior.
> 
> **Overview**
> Fixes a HIP-3 asset mapping failure where `#cachedValidatedDexs` could
be populated via the standalone preload path while `#cachedAllPerpDexs`
stayed `null`, leading to missing `perpDexIndex` during
`#buildAssetMapping`.
> 
> `#getStandaloneValidatedDexs()` now also populates
`#cachedAllPerpDexs` after a successful `perpDexs()` call, and
`#buildAssetMapping()` no longer “poisons” the shared cache with a
persistent `[null]` fallback (it uses a local fallback instead).
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
c925609. This will update automatically
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[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->