v6.2.4.0

feat(ios): support arm64 simulator runtime layers

Add the iphonesimulator-arm64 profile with simulator SDK and target flags, separate dependency directories, SDK-aware archive merging and a distinct runtime ABI stamp.

Invalidate the previous object target before building and publish its replacement atomically after compilation and merging succeed. Propagate failures so switching back after an interrupted target build cannot reuse incompatible objects.

Add CI regression coverage for target switching, compilation failures and merge failures using mock commands. Validation: 3 tests and 53 assertions pass; the pre-fix template fails both failure-path regressions. PHP/Bash syntax, PSR-12 and diff checks pass. No real Xcode build was performed.