Author IDL transforms with codama macros instead of render-time visitors

[lorisleiva]

This PR moves several IDL transforms from render-time codama.mjs visitors into codama macros on the interface crate, so the canonical idl.json carries them directly:

• The StakeInstruction discriminator is authored as a u32 via codama(enum_discriminator(size = number(u32))).
• Every instruction uses the omitted optional-account strategy via an enum-level codama(optional_account_strategy = omitted) (new in codama-rs 0.13.1).
• The four *Args tuple arguments now link to their renamed *Params defined types via codama(type = link(...)), fixing links that dangled in the committed IDL, and retiring the updateDefinedTypesVisitor.
• Two dead visitors forcing stakeState/stakeStateV2 enum sizes to u32 are removed — those enums already carry enum_discriminator attributes, so the raw IDL was already correct.
• The empty-account-list backfill in the before section is removed as redundant; the one in the rust script remains, since @codama/renderers-rust 3.1.3 renders NaN into zero-account instructions without it.

Also bumps codama/codama-macros and the pinned codama-cli to 0.13.1, and drops the ./ path workaround in the Makefile now that the CLI handles bare relative paths.

idl.json semantic diff (key-sorted comparison vs main)

• Discriminators: u8 → u32 on every instruction.
• optionalAccountStrategy: "omitted" on every instruction.
• Four of the six dangling definedTypeLinkNodes fixed (lockupArgs → lockupParams etc.); only epoch/unixTimestamp remain, resolved at render time as before.

Verification

• make generate-clients leaves a clean tree — the generated JS/Rust clients are byte-identical.
• Builds with and without --features codama; all interface + codama_schema tests pass.
• cargo fmt --check and cargo clippy --all-targets --features codama -- --deny=warnings clean.