[windows] WinRT projection: HSTRING marshalling lossy past BMP ASCII; ApplicationDataContainer.Values IMap unprojected #11614

Environment

@nativescript/core 9.1.3 (pkg.pr.new runtime abae298/cbec98bb), packaged WinUI 3 MSIX (org.octanexplat.windows61), Windows 11 x64, {N} Windows runtime alpha.

Defects verified on the packaged runtime

1. WinRT HSTRING marshalling is lossy past BMP ASCII

Windows.ApplicationModel.DataTransfer.DataPackage.SetText accepts any JS string, but the JS↔HSTRING marshalling mangles non-BMP content:

• Non-BMP code points return '?' per UTF-16 unit — writing '😀' reads back '??'; '🇯🇵' reads back '????'; 'clip--😀-🇯🇵-e\u0301-\u0000-end' reads back 'clip--??-????-e'-'.
• U+0301 combining acute maps to a codepage quote/acute char.
• Text truncates at the first U+0000 ('before\0after' reads back 'before').
• The exact mojibake is nondeterministic across identical launches — a lone '😀' returned '??' on some launches and the real '😀' on others.
• Clipboard.SetContent+Flush commits are racy: an immediate GetTextAsync can read null or stale content; a ~350 ms settle is required for deterministic read-after-write.

BMP ASCII round-trips exactly. The same JS string round-trips correctly through PathIO.WriteTextAsync/ReadTextAsync (file IO), so the loss is specific to the clipboard/string marshalling path, not general string handling.

2. ApplicationDataContainer.Values IMap surface is unprojected

Windows.Storage.ApplicationData.Current.LocalSettings.Values projects as an opaque handle — none of the IMap surface (HasKey, Lookup, Insert, Remove, First, Size) is callable; ApplicationSettings.getString throws TypeError: ... Values.HasKey is not a function and direct member calls are silent no-ops. Preferences can only be persisted through a JSON document + the working file APIs.

Happy to share the qualification fixture that produced the evidence (packaged MSIX launches mw1bskqo, mw1iafcb, mw1jqr1q).