Pull `underlyingSymbol` from on-chain instead of canonical JSON

Each entry in `cyclo.sol/canonical/cyclo-site-tokens.json` carries the underlying token's `symbol` as `underlyingSymbol`. The underlying is an ERC20 with a `symbol()` accessor — once `underlyingAddress` is read on-chain, chain together: `vault.asset()` then `asset.symbol()`. Drop the `underlyingSymbol` field from the canonical JSON.

Start by tracing the code path that reads underlyingAddress and identify where the vault asset is resolved. Chain vault.asset() to asset.symbol(), then remove underlyingSymbol from cyclo.sol/canonical/cyclo-site-tokens.json; done means the symbol is obtained on-chain and the canonical entries no longer carry that field.

Written by the indexing model from the issue text.