Write genesis data into legacy fields instead of extraConfig, fixing silently empty testnets on older nodes

[carbolymer]

Reverts the writer side of #1384. genesis create, genesis create-staked and genesis create-testnet-data write initial funds, stake pools, stake credentials, delegations and initial DReps into the top-level initialFunds/staking (Shelley) and delegs/initialDReps (Conway) fields again, not into extraConfig.

Nodes built with cardano-ledger-shelley < 1.19 do not know extraConfig and silently ignore it, so a testnet created with cardano-cli 11.2.0.0 starts with an empty UTxO set and no genesis staking, without any error. The switch to extraConfig also brought no benefit: cardano-cli only ever emitted inline (EmbeddedInjection) data, which the ledger treats identically to the legacy fields. The streaming benefit only exists for file-based injection, which nothing uses yet.

The writers now set sgExtraConfig/cgExtraConfig to SNothing explicitly: cardano-api's genesis template defaults populate them with empty injections, which would otherwise leak an empty extraConfig block into the output. This also means a template-supplied extraConfig is discarded rather than passed through - it would conflict with the generated legacy fields at node startup.

Context

The bug was found when a nightly testnet run against cli master came up "healthy" but with initialFunds: {} and all funds under extraConfig.initialFunds.data, which the node silently dropped. The first visible symptom is a funding transaction failing much later with no TxIns available - there is no error anywhere in between.

The compatibility boundary: cardano-ledger-shelley 1.19.0.0 (which introduces extraConfig) reached CHaP on 2026-07-29 as part of the node 11.1 dependency batch, so nodes <= 11.0.x are affected, while nodes on ledger >= 1.19 read either shape. Older ledgers parse the genesis with plain aeson withObject, which never rejects unknown keys, hence the silence.

The revert is lossless for every ledger that exists today: ledger's resolveInjectionSource converts legacy fields into exactly the EmbeddedInjection value the cli was constructing by hand. The legacy fields carry no deprecation pragma and initialFunds remains a mandatory key in ledger's FromJSON. The ledger's dual-read path is marked as transitional (TODO: remove this once we move over to the extraConfig fields exclusively), so extraConfig output should be reintroduced behind an explicit option once file-based streaming injection is actually used and old nodes are no longer a concern. Ideally, when the ledger drops the legacy migration, populated legacy fields should become a startup error rather than being ignored, so this failure mode stays loud.

How to trust this PR

The source changes are a byte-for-byte reversal of a91953c's hunks (verified against git show a91953cd4), plus the four explicit SNothing field updates and the removal of now-unused imports and build-depends.

All 689 cardano-cli-golden and 72 cardano-cli-test tests pass via the nix checks, and the build is clean under -Werror.

To observe the fixed behaviour:

cardano-cli conway genesis create-testnet-data \
  --testnet-magic 42 --utxo-keys 2 --pools 1 --stake-delegators 1 \
  --total-supply 10000000000000 --out-dir /tmp/testnet-out
jq '{initialFunds: (.initialFunds | length), pools: (.staking.pools | length), stake: (.staking.stake | length), hasExtraConfig: has("extraConfig")}' /tmp/testnet-out/shelley-genesis.json

Expected: initialFunds: 3, pools: 1, stake: 1, hasExtraConfig: false (on 11.2.0.0 this yields initialFunds: 0 and hasExtraConfig: true). The conway genesis likewise no longer contains an extraConfig key.

A sweep of cardano-node, cardano-api and cardano-testnet found no consumer that hand-parses extraConfig from genesis JSON; all consumption goes through ledger types, which accept both shapes.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff
• Changelog fragment added in .changes/