Fix #1: Drain stdout/stderr tasks in a finally block so they are
always awaited, even when WaitForExitAsync throws on cancellation.
PipeOutputAsync now catches OperationCanceledException internally.

Fix #2: Resolve build configuration from the AppHost's
AssemblyConfigurationAttribute (same as DcpExecutor) and pass it to
MauiBuildInfoAnnotation, so the pre-build and DCP's Run target use
the same configuration and MSBuild's incremental build is effective.

Fix #3: Add 10-minute build timeout via CancellationTokenSource so
a hung dotnet build process cannot block the semaphore forever.
BuildTimeout is an internal settable property for testability.

Fix #4: Add tests for MauiBuildInfoAnnotation (properties, nullable),
missing MauiBuildQueueAnnotation (skip), resource restart (build same
resource twice), and unexpected exception types (semaphore release).

Total: 90 tests passing (18 build queue + 72 existing).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>