fix: expose sizeof as count alias

[nahime0]

Summary

• register sizeof() with the same signature and semantics as count()
• route AOT and Magician/eval calls through the existing count implementation
• add focused native, eval, arity-diagnostic, and registry-parity coverage
• regenerate and audit the contract-derived builtin reference

Plan

1. Add the shared PHP builtin contract and backend bindings.
2. Reuse the existing typed count lowering and eval adapters.
3. Validate native, eval, registry parity, and generated builtin documentation.

Testing

• cargo build
• cargo test --test codegen_tests test_sizeof_alias_of_count
• cargo test --test codegen_tests test_eval_sizeof_alias_of_count
• cargo test --test error_tests test_error_sizeof_wrong_args
• cargo test -p elephc-magician execute_program_dispatches_sizeof_alias_of_count
• cargo test -p elephc-builtin-contract --features curl
• generated builtin docs and EIR-boundary audits
• git diff --check origin/main...HEAD

Fixes #751

  

[greptile-apps]

Too many files changed for review (1937 files, 100 file limit).