Fix WorkQueue destructor deadlock by merging into AppRuntime

[bghgary]

Fix the WorkQueue destructor deadlock by merging WorkQueue into AppRuntime and dispatching cancellation as a work item.

The Bug

WorkQueue::~WorkQueue() cancelled from the main thread via cancel() + notify_all(). The notify fired without holding the queue mutex, so if the worker thread hadn't entered condition_variable::wait() yet, the signal was lost and join() hung forever. See #146 for a deterministic repro of the deadlock against the old code.

The Fix

• Merge WorkQueue into AppRuntime: Eliminates split-lifetime issues where the worker thread could access partially-destroyed AppRuntime members during shutdown.
• Dispatch cancellation as a work item: Append(cancel) calls push() which acquires the queue mutex, so it blocks until the worker enters wait(). Push completes, notifies, worker wakes. No lost signal possible.
• Fix member declaration order: m_options now declared before the worker thread members so it outlives them during destruction.

Regression Test

Includes a deterministic test using arcana testing hooks (microsoft/arcana.cpp#59) that sleeps while holding the queue mutex before wait(). This guarantees the worker is in the vulnerable window when destruction fires. The test passes with this fix and deadlocks with the old code (#146).

Dependencies

• Add optional testing hook for blocking_concurrent_queue microsoft/arcana.cpp#59 (testing hooks, for the regression test only)

[Copilot]

Pull request overview

This PR fixes a shutdown deadlock in the JavaScript worker queue by inlining the former WorkQueue implementation into Babylon::AppRuntime and changing cancellation to be dispatched as a queued work item, then adds a deterministic regression test using arcana testing hooks to reproduce the old race.

Changes:

• Merge WorkQueue into AppRuntime (thread, dispatcher, cancellation, suspend/resume) and cancel via queued work item.
• Add a deterministic unit test (DestroyDoesNotDeadlock) guarded by ARCANA_TESTING_HOOKS.
• Update test harness / build configuration (Win32 gtest argv init; arcana fork + ARCANA_TESTING_HOOKS definition).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
Tests/UnitTests/Win32/App.cpp	Initializes gtest with argc/argv and runs tests directly.
Tests/UnitTests/Shared/Shared.cpp	Adds deterministic deadlock regression test using arcana hooks.
Core/AppRuntime/Source/WorkQueue.h	Removes standalone WorkQueue (merged into AppRuntime).
Core/AppRuntime/Source/WorkQueue.cpp	Removes standalone WorkQueue implementation.
Core/AppRuntime/Source/AppRuntime.cpp	Moves queue/thread/cancel/suspend logic into AppRuntime and cancels via queued work item.
Core/AppRuntime/Source/AppRuntime_JSI.cpp	Switches V8 JSI task runner adapter to post tasks via AppRuntime::Dispatch.
Core/AppRuntime/Include/Babylon/AppRuntime.h	Adds dispatcher/thread/cancellation members and in-class Append helper.
Core/AppRuntime/CMakeLists.txt	Removes WorkQueue sources from build.
CMakeLists.txt	Switches arcana dependency to a fork and defines ARCANA_TESTING_HOOKS when tests are enabled.

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[bghgary]

⚠️ Do not merge until microsoft/arcana.cpp#59 is merged. The arcana.cpp FetchContent currently points to bghgary/arcana.cpp. Once the upstream PR merges, update the GIT_REPOSITORY and GIT_TAG back to microsoft/arcana.cpp.