Rust + Solana (Anchor Framework)

# Rust + Solana (Anchor) Best Practices

## Program Structure
- Structure Solana programs using `Anchor` framework standards
- Place program entrypoint logic in `lib.rs`, not `main.rs`
- Organize handlers into modules (e.g., `initialize`, `update`, `close`)
- Separate state definitions, errors, instructions, and utils
- Group reusable logic under a `utils` module (e.g., account validation)
- Use `declare_id!()` to define program ID

## Anchor Framework
- Use `#[derive(Accounts)]` for all instruction contexts
- Validate accounts strictly using constraint macros (e.g., `#[account(mut)]`, `seeds`, `bump]`)
- Define all state structs with `#[account]` and `#[derive(AnchorSerialize, AnchorDeserialize)]`
- Prefer `Init`, `Close`, `Realloc`, `Mut`, and constraint macros to avoid manual deserialization
- Use `ctx.accounts` to access validated context accounts
- Handle CPI (Cross-Program Invocation) calls via Anchor’s CPI helpers

## Serialization
- Use **Borsh** or Anchor's custom serializer (not Serde) for on-chain data
- Always include `#[account(zero_copy)]` or `#[repr(C)]` for packed structures
- Avoid floating point types — use `u64`, `u128`, or fixed-point math
- Zero out or close unused accounts to reduce rent costs

## Testing
- Write tests in TypeScript using Anchor’s Mocha + Chai setup (`tests/*.ts`)
- Use `anchor.workspace.MyProgram` to load deployed contracts
- Use `provider.simulate()` to inspect failed txs
- Spin up a local validator (`anchor test`) and reset between tests
- Airdrop SOL to wallets with `provider.connection.requestAirdrop(...)`
- Validate program logs using `tx.confirmation.logMessages`

## Solana SDK (Manual)
- Use `solana_program` crate when not using Anchor (bare-metal programs)
- Carefully deserialize accounts using `AccountInfo`, `try_from_slice_unchecked`
- Use `sol