Cardano Updates

Replace nix flake check with direct test execution to prevent OOM.
Each test suite runs with +RTS -M2G to cap heap at 2GB.

The previous Arbitrary instance could generate EpochLength values up to
maxBound (4 billion) combined with epoch numbers up to 1000, causing
flatSlot to return trillions. Tests using applyN (flatSlot slot) would
hang indefinitely.

Now constrains EpochLength to 1-1000 and bounds epoch number so flatSlot
stays under ~10000 iterations.

HLS 2.9.0.0 doesn't support GHC 9.8.4. Update tools index-state
to 2026-01-20 to get HLS 2.13.0.0 which has GHC 9.8.4 support.

Replace head with pattern matching or safe alternatives in:
- db-bench.hs (benchmark labels)
- Integration tests: Byron/Migrations, Shared/Transactions,
  Shared/Wallets, Shelley/Addresses, Shelley/Migrations,
  Shelley/StakePools, Shelley/Transactions, Shelley/TransactionsNew,
  Shelley/Wallets

Replace head/tail partial functions with pattern matching or NonEmpty
alternatives in test files to avoid -Wx-partial warnings becoming errors
with -Werror.

- Add DuplicateRecordFields to Cardano.Write.Tx
- Replace partial functions in CommandLine.hs and BalanceSpec.hs

Replace head with pattern matching or safe alternatives in:
- SlottingSpec.hs
- RangeSpec.hs
- Discovery.hs

GHC 9.8.4 requires this extension when exporting types
with duplicate field names.

GHC 9.8.4 warns about head/tail as partial functions.
Also remove Ord from TxChange since TokenMap doesn't support Ord.

GHC 9.8.4 warns about head as a partial function.

GHC 9.8.4 warns about head as a partial function.

GHC 9.8.4 warns about head/tail as partial functions.
Replace tail with drop 1 and head with explicit pattern matching.

HLS 2.13.0.0 supports GHC 9.8.4.

The new cardano-api validates Plutus scripts during TxBody creation.
Random bytes from QuickCheck's arbitrary instance fail with
TxBodyPlutusScriptDecodeError. Use a minimal valid "always succeeds"
script (the UPLC lambda \_ _ _ -> ()) instead.

Fixes balance-tx test failures in Conway/Babbage balanceTx tests.

Replace head/tail partial functions with pattern matching or NonEmpty
alternatives in test files to avoid -Wx-partial warnings becoming errors
with -Werror.

Replace head with pattern matching or safe alternatives in:
- db-bench.hs (benchmark labels)
- Integration tests: Byron/Migrations, Shared/Transactions,
  Shared/Wallets, Shelley/Addresses, Shelley/Migrations,
  Shelley/StakePools, Shelley/Transactions, Shelley/TransactionsNew,
  Shelley/Wallets