Implement #NI: Expose all C API methods and bump patch version

[Sild]

Summary

• expose all 40 C ABI functions exported by the pinned TON v2026.05 headers
• document ownership and safety requirements for the 11 newly exposed functions
• add behavior-focused runtime coverage for every exported tonlib, transaction emulator, and TVM emulator method
• link the upstream root git archive required by emulator_version
• bump the crate patch version from 2026.5.0 to 2026.5.1

Validation

• exported-symbol parity: 40 upstream / 40 Rust, with no missing or Rust-only names
• cargo test (3 comprehensive suites passed)
• cargo +nightly fmt -- --check
• cargo clippy --all-targets -- -D warnings
• cargo clippy --all-targets --all-features -- -D warnings
• Rust pre-push workflow
• cargo publish --dry-run --allow-dirty
• git diff --check