Package and export Windows CEF sandbox support

[summeroff]

Summary

• consume the CEF 6533 Windows x64 revision 4 archive with the complete sandbox library
• expose CEF::Sandbox in-tree and relocatable OBS::cef-sandbox metadata in the installed development package
• gate Windows x64 sandbox packaging by platform and pointer size, independent of the CMake generator
• install the CEF headers, sandbox ABI header, and Release sandbox library required by downstream hosts
• package the complete CEF runtime/resource manifest and validate compatibility PDBs in CI
• add a create/destroy link-smoke target and pin obs-browser PR Check if the replay buffer was saved sucessfully #55
• skip only the 5.52 GB libcef.dll.pdb during legacy CAB symbol-server ingestion; it remains in the downloadable debug-symbol artifact

Dependency

• depends on Enable the CEF sandbox for Windows browser subprocesses obs-browser#55
• intentionally remains on CEF 6533 v4; CEF 6613 is a separate follow-up PR

Published test artifact

• libobs-windows64-release-32.1.1sl10cef1.7z
• SHA-256: B347C8948B820E2C822366B4DABA1BD93FDF75F47E1C6B5F0FD9E4C4995AC23D
• consumed by Host sandboxed CEF subprocesses in obs64 obs-studio-node#1779

Validation

• cmake --preset windows-x64
• Debug and RelWithDebInfo builds of obs-browser, the legacy helper, sandbox link smoke, and sandbox-selection test
• both sandbox-selection and link-smoke executables pass in both configurations
• full local build/install and downstream package-consumer checks
• generator-independent package export reviewed for Visual Studio and Ninja compatibility

Security gate

Source and command-line checks do not prove that Chromium children received restricted tokens and job-object confinement. Merge readiness for the complete stack still requires process-token and job-object evidence from the runtime matrix.

[summeroff]

Superseded by #775 after renaming the source branch to remove the internal issue identifier. The commits and review fixes are preserved there.