feat: expose functionality to start benchmarking manually

[tsdevshop]

Description

• Allows useBenchmark and useFlatListBenchmark to be started manually. This supports runtime benchmarking - an in-app button or other input can be used to programmatically start a benchmark.
• Updates the code to use the publicly exposed imperative methods on the Flashlist instance, instead of using the internal recyclerlistview_unsafe property.

Reviewers’ hat-rack 🎩

TBC

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Screenshots or videos (if needed)

TBC

[Copilot]

Pull Request Overview

This PR adds support for manually triggering benchmarks at runtime and replaces internal recyclerlistview_unsafe accesses with the public imperative methods on the FlashList instance.

• Expose startBenchmark function and isBenchmarkRunning flag; introduce startManually param to defer automatic start
• Swap out recyclerlistview_unsafe for getWindowSize / getChildContainerDimensions
• Update fixture examples to use new hook APIs

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/benchmark/useFlatListBenchmark.ts	Add state, startBenchmark callback, manual start
src/benchmark/useBenchmark.ts	Mirror manual-start API; swap internal RecyclerListView calls
src/benchmark/useBlankAreaTracker.ts	Remove recyclerlistview_unsafe; use public FlashList methods
fixture/react-native/src/twitter/TwitterBenchmark.tsx	Switch from useFlatListBenchmark to useBenchmark
fixture/react-native/src/ManualFlatListBenchmarkExample.tsx	Add manual FlatList benchmark example
fixture/react-native/src/ManualBenchmarkExample.tsx	Add manual FlashList benchmark example

Comments suppressed due to low confidence (2)

src/benchmark/useFlatListBenchmark.ts:1

• [nitpick] Add a JSDoc comment for the new startManually and returned { startBenchmark, isBenchmarkRunning } API so that users understand its purpose and return shape.

import { useCallback, useEffect, useRef, useState } from "react";

src/benchmark/useFlatListBenchmark.ts:47

• The function runScrollBenchmark is invoked but not imported in this file. Add import { runScrollBenchmark } from './AutoScrollHelper'; or from the correct module to avoid a runtime ReferenceError.

        await runScrollBenchmark(

[Copilot]

[nitpick] Wrap the body of runBenchmark in a try/finally block so that setIsBenchmarkRunning(false) always runs even if an exception is thrown, ensuring the hook state is correctly reset.

[Copilot]

[nitpick] Consider moving this call into a finally block inside runBenchmark to guarantee that benchmarking state is reset even if callback or metrics gathering throws an error.