Fix error message loss in IAsyncOperation by replacing std::runtime_error with winrt::hresult_error

[Copilot]

Description

Type of Change

• Bug fix (non-breaking change which fixes an issue)

Why

GetJavaScriptFromServerAsync was updated to return winrt::Windows::Foundation::IAsyncOperation<IBuffer>, but error paths still threw std::runtime_error. C++/WinRT converts non-WinRT exceptions to a generic HRESULT when propagating failures through IAsyncOperation::get(), silently dropping the detailed packager/HTTP error text that callers rely on for diagnostics.

What

vnext/Shared/DevSupportManager.cpp / DevSupportManager.h

• Converted GetJavaScriptFromServerAsync return type from std::future<std::pair<std::string, bool>> to IAsyncOperation<IBuffer>
• Converted PollForLiveReload return type from std::future<HttpStatusCode> to IAsyncOperation<HttpStatusCode>
• Replaced throw std::runtime_error(error) in HRESULT failure path with throw winrt::hresult_error(hr, winrt::to_hstring(error)) — preserves both the original HRESULT code and message
• Replaced throw std::runtime_error(error) in HTTP error path with throw winrt::hresult_error(E_FAIL, winrt::to_hstring(error))
• Removed the catch block that was re-throwing winrt::hresult_error as std::runtime_error, which downgraded the error
• Updated GetJavaScriptFromServer to unpack the IBuffer result and catch winrt::hresult_error for error reporting
• Removed #include <future> (no longer used)

Before (error text lost at .get()):

throw std::runtime_error(error); // C++/WinRT maps this to a generic HRESULT, dropping `error`

After (error text preserved):

throw winrt::hresult_error(hr, winrt::to_hstring(error)); // HRESULT + message both survive .get()

Screenshots

N/A

Testing

No new tests added; this is a targeted fix to error-propagation behavior in the WinRT async layer.

Changelog

Should this change be included in the release notes: no