18-decimal ERC-style tokens malfunction in liquidity module pools

[saint-Joy]

Current Behavior

Tokens with 18 decimals (e.g. gravETH and similar ERC-20 bridged tokens) do not work correctly in x/liquidity module pools. Swaps involving these tokens fail randomly (~80% failure rate, see #663 for related overflow evidence).

Expected Behavior

Pools containing 18-decimal tokens should handle deposits, withdrawals, and swaps correctly, same as 6-decimal native tokens.

Hypothesis

The liquidity module batch matching arithmetic likely truncates or overflows when operating on amounts with 18-decimal precision. The module was designed for 6-decimal Cosmos-native tokens.

Reproduction

1. Create a pool with a high-decimal IBC token (e.g. gravETH) and a native token
2. Attempt swaps in both directions
3. Observe random failures

Fix Path

Requires chain upgrade — module-level arithmetic fix in batch execution.

Related: #663 (swap overflow with large amounts)