fix(perps): Incorrect PnL and order size displayed in perp market page after SL execution (#28593)

## **Description**

The Activity page showed incorrect (lower) PnL and size for trades
executed via multiple sub-fills (e.g. a Stop Loss split into 10 partial
fills). The `mergedTransactions` useMemo in `usePerpsTransactionHistory`
aggregated WebSocket fills into `PerpsTransaction` objects before
merging with REST data, allowing the WS partial snapshot to overwrite
the correctly aggregated REST result. The fix merges raw `OrderFill`
objects at the fill level first (same pattern as `usePerpsHomeData`),
then transforms once on the complete set.

## **Changelog**

CHANGELOG entry: Fixed a bug where the Activity page showed incorrect
PnL and order size for trades executed via multiple partial fills (e.g.
Stop Loss).

## **Related issues**

Fixes:
[TAT-2483](https://consensyssoftware.atlassian.net/browse/TAT-2483)

## **Manual testing steps**

```gherkin
Feature: Activity page PnL correctness after multi-fill trade

  Scenario: Stop Loss execution with multiple sub-fills shows correct aggregated PnL
    Given wallet is unlocked and perps feature is enabled
    And a Stop Loss order was executed via multiple partial sub-fills

    When user navigates to Activity page → Trades tab

    Then the trade row PnL matches the value shown on the market detail page
    And no TypeError appears in Metro logs
    And no BUG_MARKER fires in Metro logs
```

## **Screenshots/Recordings**


### **Before**

<!-- before.mp4 — Activity page showing incorrect PnL (WS partial
snapshot overwrites REST aggregate) -->

### **After**

<!-- after.mp4 — Activity page showing correct PnL after raw-fill-level
merge -->

## **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.

## **Validation Recipe**

<details>
<summary>recipe.json — TAT-2483: Activity page shows correct aggregated
PnL after multi-fill trade</summary>

```json
{
  "title": "TAT-2483: Activity page shows correct aggregated PnL after multi-fill trade",
  "jira": "TAT-2483",
  "acceptance_criteria": [
    "Activity page Trades tab loads without error",
    "Trade transactions are present in the Trades tab",
    "No BUG_MARKER fires in metro logs (WS overwrite does not corrupt aggregated data)",
    "No TypeError or undefined errors in metro logs during Activity page render"
  ],
  "validate": {
    "static": ["yarn lint:tsc"],
    "workflow": {
      "pre_conditions": ["wallet.unlocked", "perps.feature_enabled"],
      "entry": "nav-activity",
      "nodes": {
        "nav-activity": {
          "action": "navigate",
          "target": "PerpsActivity",
          "params": { "redirectToPerpsTransactions": true },
          "next": "wait-render"
        },
        "wait-render": {
          "action": "wait_for",
          "route": "PerpsActivity",
          "next": "check-no-errors"
        },
        "check-no-errors": {
          "action": "log_watch",
          "window_seconds": 5,
          "must_not_appear": ["BUG_MARKER", "TypeError", "undefined is not an object"],
          "watch_for": ["User fills received"],
          "next": "check-state"
        },
        "check-state": {
          "action": "eval_sync",
          "expression": "JSON.stringify(Engine.context.PerpsController.state.accountState)",
          "assert": { "operator": "not_null" },
          "next": "screenshot-activity"
        },
        "screenshot-activity": {
          "action": "screenshot",
          "filename": "evidence-activity-trades.png",
          "next": "done"
        },
        "done": {
          "action": "end",
          "status": "pass"
        }
      }
    }
  }
}
```

</details>

[TAT-2483]:
https://consensyssoftware.atlassian.net/browse/TAT-2483?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Changes the perps activity/trade merging logic to merge raw REST and
WebSocket fills before transforming, which affects user-facing PnL/size
calculations and deduplication across multiple screens.
> 
> **Overview**
> Fixes incorrect trade PnL/size for multi-subfill executions (e.g.,
Stop Loss/Take Profit) by **merging REST and WebSocket data at the raw
`OrderFill` level before transforming into `PerpsTransaction`s** in
`usePerpsTransactionHistory`.
> 
> Extracts the fill dedupe/merge behavior into a shared
`mergeOrderFills` helper (preserving REST
`detailedOrderType`/`liquidation` when WS lacks it) and reuses it in
`usePerpsHomeData` and `usePerpsMarketFills`. Updates transaction
history tests to exercise the real merge behavior and to assert ordering
and `detailedOrderType` preservation.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
6645108. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: abretonc7s

app/components/UI/Perps/hooks/usePerpsHomeData.ts

@@ -16,7 +16,10 @@ import {
   type SortField,
 } from '@metamask/perps-controller';
 import type { PerpsTransaction } from '../types/transactionHistory';
-import { transformFillsToTransactions } from '../utils/transactionTransforms';
+import {
+  transformFillsToTransactions,
+  mergeOrderFills,
+} from '../utils/transactionTransforms';
 import Engine from '../../../../core/Engine';
 import { HOME_SCREEN_CONFIG } from '../constants/perpsConfig';
 import { selectPerpsWatchlistMarkets } from '../selectors/perpsController';
@@ -123,40 +126,10 @@ export const usePerpsHomeData = ({
     };
   }, [isConnected, isInitialized]);
 
-  // Merge REST + WebSocket fills with deduplication
-  // Live fills take precedence over REST fills (more up-to-date)
-  const mergedFills = useMemo(() => {
-    // Use Map for efficient deduplication
-    const fillsMap = new Map<string, OrderFill>();
-
-    // Add REST fills first
-    for (const fill of restFills) {
-      const key = `${fill.orderId}-${fill.timestamp}-${fill.size}-${fill.price}`;
-      fillsMap.set(key, fill);
-    }
-
-    // Add live fills (overwrites duplicates from REST - live data is fresher)
-    // Preserve detailedOrderType from REST fills since WS fills lack it
-    for (const fill of liveFills) {
-      const key = `${fill.orderId}-${fill.timestamp}-${fill.size}-${fill.price}`;
-      const existing = fillsMap.get(key);
-      if (existing?.detailedOrderType && !fill.detailedOrderType) {
-        fillsMap.set(key, {
-          ...fill,
-          detailedOrderType: existing.detailedOrderType,
-          ...(existing.liquidation &&
-            !fill.liquidation && { liquidation: existing.liquidation }),
-        });
-      } else {
-        fillsMap.set(key, fill);
-      }
-    }
-
-    // Convert back to array and sort by timestamp descending (newest first)
-    return Array.from(fillsMap.values()).sort(
-      (a, b) => b.timestamp - a.timestamp,
-    );
-  }, [restFills, liveFills]);
+  const mergedFills = useMemo(
+    () => mergeOrderFills(restFills, liveFills),
+    [restFills, liveFills],
+  );
 
   // Transform merged fills to PerpsTransaction format for activity display
   const tradesOnly = useMemo(

app/components/UI/Perps/hooks/usePerpsMarketFills.ts

@@ -2,6 +2,7 @@ import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import { useSelector } from 'react-redux';
 import { usePerpsLiveFills } from './stream';
 import { PERPS_CONSTANTS, type OrderFill } from '@metamask/perps-controller';
+import { mergeOrderFills } from '../utils/transactionTransforms';
 import Engine from '../../../../core/Engine';
 import Logger from '../../../../util/Logger';
 import { ensureError } from '../../../../util/errorUtils';
@@ -133,34 +134,14 @@ export const usePerpsMarketFills = ({
   }, [fetchRestFills]);
 
   // Merge REST + WebSocket fills with deduplication, filtered by symbol
-  // Live fills take precedence over REST fills (more up-to-date)
-  const fills = useMemo(() => {
-    // Use Map for efficient deduplication
-    const fillsMap = new Map<string, OrderFill>();
-
-    // Add REST fills first
-    for (const fill of restFills) {
-      // Only add fills for the requested symbol
-      if (fill.symbol === symbol) {
-        const key = `${fill.orderId}-${fill.timestamp}-${fill.size}-${fill.price}`;
-        fillsMap.set(key, fill);
-      }
-    }
-
-    // Add live fills (overwrites duplicates from REST - live data is fresher)
-    for (const fill of liveFills) {
-      // Only add fills for the requested symbol
-      if (fill.symbol === symbol) {
-        const key = `${fill.orderId}-${fill.timestamp}-${fill.size}-${fill.price}`;
-        fillsMap.set(key, fill);
-      }
-    }
-
-    // Convert back to array and sort by timestamp descending (newest first)
-    return Array.from(fillsMap.values()).sort(
-      (a, b) => b.timestamp - a.timestamp,
-    );
-  }, [restFills, liveFills, symbol]);
+  const fills = useMemo(
+    () =>
+      mergeOrderFills(
+        restFills.filter((f) => f.symbol === symbol),
+        liveFills.filter((f) => f.symbol === symbol),
+      ),
+    [restFills, liveFills, symbol],
+  );
 
   return {
     fills,