feat(go-runtime): add proof verification syscalls

[felicityin]

I added Go zkVM runtime support for deferred proof verification.

The change introduces Go bindings and MIPS syscall stubs for:

• VERIFY_ZKM_PROOF
• COMMIT_DEFERRED_PROOFS

I also added runtime helpers to:

• verify a subproof from Go code using a subprogram vk digest and public-values digest
• commit the accumulated deferred proof digest during runtime exit

This lets Go guest programs, such as keeper-agg, participate in the same proof-carrying aggregation flow as the Rust guests.