TICKET: WP-6284

Fix s390x endianness issue in Solana transaction verification

Problem

On s390x (big-endian) architecture, @solana/web3.js incorrectly reads Solana's little-endian u64 amounts as big-endian during transaction parsing in Transaction.fromRawTransaction(). The library uses Node.js Buffer methods that are architecture-dependent, causing byte order misinterpretation.

This results in corrupted amounts when explainTransaction() is called:

• Small amounts (e.g., 10,000 lamports) → appear as huge values (~1.16×10^18 lamports)
• Large amounts (e.g., ~5×10^17 lamports) → appear as tiny values (7 lamports)

Both cases cause verifyTransaction() to fail when comparing parsed transaction amounts against user-provided recipients.

Root Cause

• Solana stores amounts as u64 in little-endian format
• @solana/web3.js parser uses Buffer reads that respect architecture endianness
• On s390x, Buffer reads are big-endian by default
• Result: Parser consistently reads all amounts with wrong byte order

Solution

Added getAmountBasedOnEndianness() helper function that:

1. Detects s390x architecture via process.arch
2. Byte-swaps all amounts to undo the parser's incorrect endianness interpretation
3. Returns amounts unchanged on other architectures

Applied in verifyTransaction() when:

• Comparing transaction outputs against user-provided recipients
• Summing output amounts for total validation