Fix a second batch of v22 regen regressions (CS1750/CS0182/CS0102/CS0535/CS0246 + ref readonly)

[tannergooding]

Fixes a second batch of v22.1.8 (clang 22.1.8) regressions found regenerating terrafx.interop.windows. Each is an independent codegen bug with a focused commit carrying its fix, a regression test, and unified baselines. All six were verified against faithful synthetic repros with the release generator, and the full generator suite is green (4164 passed, 0 warnings).

Bug	Code	Symptom
B1	CS1750	unsigned default parameter drops the (uint) cast
B2	CS0182	transparent-struct default wrapped in a non-const cast
A	CS0102	__uuidof constant alias emits a duplicate IID
E	(silent)	ref readonly dropped from GUID #define aliases
C	CS0535	multi-level COM inheritance drops the immediate base's members
D	CS0246	dropped using System.Numerics; while still using Matrix4x4

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B1 — unsigned default parameter drops the (uint) cast (CS1750)

A bare negative literal default on an unsigned parameter emitted unchecked(-1), which is int and won't bind to the uint parameter. An explicit UINT(-1) default was unaffected; only a bare -1 lost the cast.

extern "C" void MyFunction(unsigned int value = -1);

Now emits uint value = unchecked((uint)(-1)).

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B2 — transparent-struct default wrapped in a non-const cast (CS0182)

A transparent-struct-typed default was wrapped in ((HRESULT)(0)), which isn't a constant expression and fails inside DefaultParameterValue. Emit the bare constant (DefaultParameterValue(0)), matching v21.

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A — __uuidof constant alias emits a duplicate IID (CS0102)

A static const IID& alias initialized from __uuidof names the same IID_ symbol the interface's uuid already emits via _uuidsToGenerate, so a second definition was generated (same member name twice, plus a Guid*-typed field assigned a Guid). Skip the redundant declaration.

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E — ref readonly dropped from GUID #define aliases

For #define IID_X IID_Y aliases the generator kept a => ref IID_Y body but lost the ref readonly on the return type, leaving a by-value Guid return paired with a ref body — semantically a copy, and CS8149 in isolation. Preserve the reference so the alias stays zero-copy.

-public static Guid IID_IOInet => ref IID_IInternet;
+public static ref readonly Guid IID_IOInet => ref IID_IInternet;

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C — multi-level COM inheritance drops the immediate base's members (CS0535)

IStreamAsync : IStream : ISequentialStream : IUnknown. When the intermediate base is reached through a forward typedef struct IStream IStream; (as MIDL interfaces are declared), clang binds it to a non-definition redeclaration whose members were dropped — so IStreamAsync flattened IUnknown/ISequentialStream then jumped straight to its own member, skipping IStream's Seek…Clone. Resolve the record to its definition so every inherited vtbl slot flattens in order.

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D — dropped using System.Numerics; while still using Matrix4x4 (CS0246)

A namespaced type (System.Numerics.Matrix4x4) used only as a generic-pointer-wrapper template argument dropped its using, leaving the Matrix4x4 reference unresolved. Keep the using.

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Baselines are unified to the repo convention: B1/B2 collapse to a single {Mode} file (identical across all 16 variants); A/E/C/D collapse to {Mode} + {Mode}.Compatible (the Compatible config differs only by down-level codegen — collection expressions vs new byte[], InlineArray vs fixed).