Add manual Pimax Play Shell relaunch

[Zaknin]

Summary

• contain the Pimax relaunch JSON command inside a hidden child process with piped stdout/stderr
• keep the TUI responsive while the relaunch runs and show an acknowledgement result dialog
• document the Phase 30A validation and Phase 30A.1 console-containment fix

Validation

• dotnet test .\PimaxVrcSupervisor.Tests\PimaxVrcSupervisor.Tests.csproj
• cargo fmt --check
• cargo test
• dotnet build .\PimaxVrcSupervisor\PimaxVrcSupervisor.csproj -c Release
• dotnet build .\PimaxVrcSupervisor.ConfigEditor\PimaxVrcSupervisor.ConfigEditor.csproj -c Release
• dotnet build .\PimaxVrcSupervisor.SteamVrHost\PimaxVrcSupervisor.SteamVrHost.csproj -c Release
• cargo build --release
• python -m mkdocs build --strict
• git diff --check