Add archived view factory support

[Kyle-Ye]

Summary

• Add platform view factory rendering and decoder plumbing.
• Add archived view host/core metadata support.
• Add CoreText composition language compatibility support.
• Fix Linux build compatibility for archived view host SPI and Swift 6.3 test compilation.

[augmentcode]

🤖 Augment PR Summary

Summary: Enables archived view factory support by wiring platform view factories into rendering and adding archive host/metadata plumbing.

Changes:

• Adds `archiveHost` lookup on `ProtobufEncoder` and uses it to report factory-encoding failures
• Implements `CodableViewFactory` protobuf encode/decode using registered `ViewDecoders`
• Adds `ArchivedViewCore.Metadata` for versioning, attachment indices, archive ID, deployment version, and language/composition defaults
• Introduces archived-view host SPI types (`_ArchivedViewHostDelegate`, host/state protocols, proxies) for future writer integration
• Replaces platform layer/view factory render stubs with a warning + missing-platform-view placeholder when rendering is not ignored
• Materializes stable-identity maps on demand by unioning active scope maps
• Updates CoreText composition-language shim to provide a non-CoreText fallback and C linkage wrappers
• Fixes a Swift 6.3 test closure capture typo (`ideal`)

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[augmentcode]

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[codecov]

Codecov Report

❌ Patch coverage is 0.79365% with 125 lines in your changes missing coverage. Please review.
✅ Project coverage is 25.99%. Comparing base (e3c1c83) to head (2130772).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...s/OpenSwiftUICore/Render/PlatformViewFactory.swift	0.00%	50 Missing ⚠️
...penSwiftUICore/View/Archive/ArchivedViewCore.swift	0.00%	35 Missing ⚠️
...penSwiftUICore/View/Archive/ArchivedViewHost.swift	0.00%	20 Missing ⚠️
...ender/DisplayList/DisplayList_StableIdentity.swift	6.25%	15 Missing ⚠️
...rces/OpenSwiftUICore/Render/PlatformDrawable.swift	0.00%	3 Missing ⚠️
...penSwiftUICore/Data/Protobuf/ProtobufEncoder.swift	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #914      +/-   ##
==========================================
- Coverage   26.04%   25.99%   -0.06%     
==========================================
  Files         717      719       +2     
  Lines       50569    50668      +99     
==========================================
- Hits        13173    13169       -4     
- Misses      37396    37499     +103     

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