feat: implement surfnet_writeProgram cheatcode (#319)

[29deepanshutyagi]

✅ Implemented surfnet_writeProgram cheatcode

Hi @lgalabru ,
I’ve completed the implementation for surfnet_writeProgram as described in this issue - #319

🧩 Summary

Added a new RPC method surfnet_writeProgram to support chunked program uploads with offset-based writes.

This allows writing large programs (up to 5 MB per RPC call) directly to program data accounts — without requiring signatures or buffer accounts.

Automatically creates program and program-data accounts if missing, preserves loader metadata, and maintains rent exemption after expansion.

⚙️ Key Features

Write program data in small or large chunks using an offset.

No signature or buffer creation needed — writes directly to account data.

Replicates Solana’s upgradeable loader semantics (Program + ProgramData).

Automatically recalculates rent-exempt lamports on resize.

Fully validated inputs (pubkey, hex data, offsets).

🧪 Tests

Added 17 comprehensive tests, all passing ✅:

Sequential, non-sequential, and overlapping writes

Auto account creation

Invalid input handling

Rent recalculation

Large 1 MB write

Empty and single-byte write

issue #319

[29deepanshutyagi]

@MicaiahReid , kindly review this pr

[lgalabru]

Thanks @29deepanshutyagi, we'll look into this!

[MicaiahReid]

This is awesome, thanks @29deepanshutyagi!

I did a minor refactor, but kept nearly all of your logic. I did the following:

• move logic out of cheatcodes file and into locker.rs (we try to keep the rpc files clean and add all reusable logic to locker). I was able to use all of the code you wrote, it was awesome!
• added the optional authority field to be able to write the program authority

[lgalabru]

Thank you @29deepanshutyagi 🙏

[29deepanshutyagi]

Thank you @MicaiahReid and @lgalabru for the quick review and feedback! 🙏

@MicaiahReid - Thanks for taking the time to refactor and improve the code structure. Moving the logic to locker.rs makes total sense for keeping the RPC files clean, and adding the optional authority field is a great enhancement I hadn't considered.

Please Let me know if there's anything else I can help with regarding this issue