Revert CMake pin (#375) and properly fix HEADERS file set on FRAMEWORK target #376

Context

CMake 4.2.x (the current default on GitHub's macos-latest runners) rejects our weak-node-api build with:

CMake Error in CMakeLists.txt:
  The file set "HEADERS", of type "HEADERS", is incompatible with the
  "FRAMEWORK" target "weak-node-api".

As a temporary unblock, #375 (and the unit-tests pin in #374) pins CMake to 4.1.2 on macOS CI, which still tolerates this configuration. That's a workaround, not a fix — it freezes our macOS CI on an old CMake and will break again when 4.1.2 becomes unavailable or when contributors run a newer local CMake.

Root cause

packages/weak-node-api/CMakeLists.txt attaches headers to the same target two ways:

• Modern FILE_SET HEADERS — lines 16-24
• Legacy framework PUBLIC_HEADER — line 38, inside the if(APPLE) block that also sets FRAMEWORK TRUE (line 32)

CMake 4.2 made a HEADERS file set incompatible with a FRAMEWORK target, so setting both on the Apple build is now an error.

Proper fix

Ensure we don't declare a HEADERS file set while building a framework. Options to explore:

• On Apple (FRAMEWORK TRUE), rely solely on PUBLIC_HEADER and avoid the FILE_SET HEADERS; on other platforms keep FILE_SET HEADERS.
• Or drop PUBLIC_HEADER and use the file set's own framework/install integration if it covers our XCFramework packaging needs.

Whichever path, verify the produced macOS .framework still contains the expected public headers and the XCFramework packaging is unchanged.

Acceptance criteria

• weak-node-api configures and builds on macOS with the runner's default CMake (no version pin).
• Revert the macOS CMake pin added in ci: pin CMake on macOS weak-node-api tests #375 (and reassess the unit-tests pin from Fix main CI: commit ferric Cargo.lock and pin macOS CMake #374).
• macOS .framework / XCFramework still ships the correct public headers.

References

• Workaround PR: ci: pin CMake on macOS weak-node-api tests #375
• Related pin: Fix main CI: commit ferric Cargo.lock and pin macOS CMake #374
• packages/weak-node-api/CMakeLists.txt lines 16-24 (FILE_SET HEADERS) and 38 (PUBLIC_HEADER)