Deterministic test proving WorkQueue destructor deadlock

[bghgary]

Deterministic test proving the AppRuntime destructor has a deadlock race condition.

The Bug

WorkQueue::~WorkQueue() cancels from the main thread via cancel() + notify_all(). The notify fires without holding the queue mutex, so if the worker thread hasn't entered condition_variable::wait() yet, the signal is lost and join() hangs forever.

How This Test Works

Uses arcana testing hooks (microsoft/arcana.cpp#59) to sleep while holding the queue mutex right before wait(). This guarantees the worker is between the condition check and wait() when the destructor fires.

• Current code (broken): cancel() + notify_all() don't need the mutex, so they fire and the notification is lost while the worker sleeps. Worker enters wait() with no pending signal. Deadlock.
• Fixed code: Merges WorkQueue into AppRuntime and dispatches cancellation as a work item via Append(). push() needs the mutex, so it blocks until the worker enters wait(). Push completes, notifies, worker wakes. No deadlock.

Expected Result

This PR should FAIL CI -- the test will detect the deadlock via a 5-second timeout on iteration 0.

Changes

All additive, no production code modified:

• CMakeLists.txt: Point arcana at fork with testing hooks
• Tests/UnitTests/CMakeLists.txt: Enable ARCANA_TESTING_HOOKS for test target
• Tests/UnitTests/Android/.../CMakeLists.txt: Enable ARCANA_TESTING_HOOKS for Android test target
• Tests/UnitTests/Shared/Shared.cpp: Add DestroyDoesNotDeadlock test (guarded by ARCANA_TESTING_HOOKS)
• Tests/UnitTests/Win32/App.cpp: Pass argc/argv to gtest for --gtest_filter support

Dependencies

• Add optional testing hook for blocking_concurrent_queue microsoft/arcana.cpp#59 (testing hooks)

[Copilot]

Pull request overview

Adds a deterministic unit test that reproduces a WorkQueue/AppRuntime destructor deadlock by leveraging Arcana “before wait” testing hooks, and updates the Windows unit-test entrypoint to support standard gtest CLI arguments.

Changes:

• Switches the arcana.cpp FetchContent dependency to a fork that includes testing hooks and defines ARCANA_TESTING_HOOKS when tests are enabled.
• Adds a new AppRuntime.DestroyDoesNotDeadlock test (guarded by ARCANA_TESTING_HOOKS) that attempts to detect the destructor deadlock via timeouts.
• Updates Win32 unit test main to pass argc/argv into GoogleTest initialization and run tests via RUN_ALL_TESTS().

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
CMakeLists.txt	Points Arcana dependency to a fork and globally defines ARCANA_TESTING_HOOKS under JSRUNTIMEHOST_TESTS.
Tests/UnitTests/Shared/Shared.cpp	Adds a new deterministic deadlock-repro test using Arcana testing hooks.
Tests/UnitTests/Win32/App.cpp	Updates test entrypoint to initialize gtest with argc/argv and run tests directly.

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[bghgary]

Superseded by #147 which is now merged. This PR served its purpose demonstrating the deadlock with the old code.