[ratfreezone-lab]

Summary

• Update source-build requirements to Swift 6.0 / Xcode 16+ and clarify the macOS deployment target.
• Correct the lowercase prefix installation option and document universal build behavior.
• Document the verified RELEASEBUILDDIR workaround, cleanup commands, and distribution-signing requirements.

Verification

• make succeeded and produced arm64 and x86_64 architectures.
• Default make install failed because this toolchain used .build/out/Products/Release/xcodes rather than the Makefile’s expected .build/apple/Products/Release/xcodes.
• Installation into a temporary prefix succeeded with a RELEASEBUILDDIR override; version returned 2.1.0 and --help succeeded.
• The x86_64 deprecation warning for the active macOS 27.0 deployment target did not prevent building.
• Temporary installations and build artifacts were removed afterward.
• git diff --check passed. The test suite was not run.

Agent context

Warp conversation

Co-Authored-By: Warp agent@warp.dev