Migrate existing IDL presets off local format_arg_value (charset-safety gap for array/struct args)

[prasanna-anchorage]

Background

While reviewing #375 (which adds core::arg_rendering::format_arg_value — a shared, charset-safe, type-aware arg renderer used by the new Marginfi preset), I checked how the 17 existing IDL-based presets currently render instruction args. None of them use a shared helper — each has its own local, copy-pasted format_arg_value:

// e.g. kamino_vault, meteora_dlmm, onre_app, kamino_farms, kamino_limit, meteora_damm_v2
fn format_arg_value(value: &serde_json::Value) -> String {
    match value {
        serde_json::Value::String(s) => s.clone(),
        other => other.to_string(),
    }
}

// e.g. jupiter_perps, kamino_borrow, drift, jupiter_earn, squads_multisig,
// exponent_finance, neutral_trade, jupiter_borrow, orca_whirlpool
fn format_arg_value(value: &serde_json::Value) -> String {
    match value {
        serde_json::Value::String(s) => s.clone(),
        serde_json::Value::Number(n) => n.to_string(),
        serde_json::Value::Bool(b) => b.to_string(),
        serde_json::Value::Null => "null".to_string(),
        other => other.to_string(),
    }
}

Presets: kamino_vault, jupiter_perps, kamino_borrow, meteora_dlmm, drift, onre_app, jupiter_earn, kamino_farms, squads_multisig, kamino_limit, exponent_finance, meteora_damm_v2, neutral_trade, metadao_conditional_vault, jupiter_borrow, orca_whirlpool, metadao_futarchy.

The problem

For any arg whose serde_json::Value is an Array or Object (byte arrays, structs, enum payloads, nested IDL types), the fallback arm calls other.to_string() / value.to_string(), which is serde_json::Value's Display impl — i.e. it serializes the value as literal JSON, quotes and all (e.g. ["a","b"], {"side":"buy"}).

That's a charset-safety violation risk: SignablePayload::validate_charset rejects " and \ in rendered field text. Any preset among the 17 above that decodes an instruction with an array- or struct-typed arg would emit a fallback string containing ", which the crate's own charset validation is specifically designed to catch and reject — meaning either (a) it's never been hit because none of the fuzzed/tested transactions for these presets exercise an array/struct arg, or (b) it's silently failing charset validation somewhere already. Either way it's a live gap, not a hypothetical one, since it doesn't depend on any future IDL — it's live in main today for these 17 presets.

Suggested fix

Migrate these presets off their local format_arg_value onto the shared, charset-safe, type-aware version added in core::arg_rendering by #375 (plus the find_idl_instruction/arg_types_for helpers proposed as a follow-up there). This fixes the charset-safety gap and gets type-driven byte-array rendering (no more mis-rendering an array of small numbers as a JSON blob) in one pass, rather than fixing each preset's local copy separately.

Scope note

Deliberately kept out of #375 itself — that PR's own description says "existing presets keep their current renderers untouched," and this touches ~17 files rather than the one new preset. Tracking here so it doesn't get lost.