Remove WINRT_EXPORT in Component.g.cpp

[YexuanXiao]

The WINRT_EXPORT namespace block here only contains definitions of the component's member functions, so it is meaningless.

[Copilot]

Pull request overview

Updates the C++/WinRT code generator to omit WINRT_EXPORT on the namespace winrt::<type_namespace> block in generated component .g.cpp files, since that block contains only member-function definitions and the export annotation is not meaningful there.

Changes:

• Switch component .g.cpp generation to open namespace winrt::<ns> without WINRT_EXPORT.
• Add a dedicated writer helper to emit a non-exported winrt::<ns> namespace wrapper.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
cppwinrt/component_writers.h	Uses the new non-export namespace wrapper for generated component .g.cpp member definitions.
cppwinrt/code_writers.h	Adds wrap_type_namespace_without_export helper to emit namespace winrt::<ns> without WINRT_EXPORT.