Add evaluateTransaction to Cardano.Api.Experimental

[carbolymer]

Context

Closes #1204

cardano-api has individual building blocks for transaction evaluation (evaluateTransactionExecutionUnits, evaluateTransactionFee, evaluateTransactionBalance) but no single function that runs the full evaluate execution units, compute fee, check balance pipeline on a signed transaction.

cardano-rpc's evalTxMethod filled this gap by inlining the pipeline with ledger internals directly. This PR extracts that logic into a reusable cardano-api function.

Changes

• cardano-api: Add evaluateTransaction and evaluateSignedTx to Cardano.Api.Experimental, composing script evaluation, fee computation via setMinFeeTxUtxo, and balance checking into a single pure function. Add TxEvaluationResult result type with fee, per-redeemer execution units, and balance fields.
• cardano-rpc: Refactor evalTxMethod to call Exp.evaluateTransaction instead of inlining the pipeline (-46 lines).
• Tests: Three new property tests for evaluateTransaction - positive fee, empty execution units for script-free transactions, and mempty balance for transactions balanced by calcMinFeeRecursive.

How to trust this PR

The core function (evaluateTransaction in Fee.hs) is a direct extraction of the logic previously in Eval.hs lines 83-137. The pipeline is:

1. evaluateTransactionExecutionUnits - run scripts
2. Substitute evaluated ExUnits into the redeemer map (failed redeemers keep client-supplied units)
3. setMinFeeTxUtxo - compute fee for the concrete signed tx with UTxO context
4. evalBalanceTxBody - check the balance

Checklist

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

[Copilot]

Pull request overview

Extracts the "evaluate execution units → compute min fee → check balance" pipeline that was inlined in cardano-rpc's evalTxMethod into a reusable Cardano.Api.Experimental function (evaluateTransaction, plus a SignedTx-flavoured wrapper evaluateSignedTx), introduces a TxEvaluationResult record, and refactors evalTxMethod to call the new function. Adds three property tests covering the new function.

Changes:

• Add evaluateTransaction / evaluateSignedTx / TxEvaluationResult to Cardano.Api.Experimental.Tx.Internal.Fee and re-export through Cardano.Api.Experimental.Tx and Cardano.Api.Experimental under a new "Transaction evaluation" section.
• Refactor evalTxMethod in cardano-rpc to delegate the pipeline to the new function (−46 lines).
• Add property tests for fee positivity, empty ExUnits for script-free txs, and mempty balance for balanced txs; add two Herald changelog fragments (feature for cardano-api, refactoring for cardano-rpc).

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
cardano-api/src/Cardano/Api/Experimental/Tx/Internal/Fee.hs	Adds TxEvaluationResult data type and evaluateTransaction orchestration function.
cardano-api/src/Cardano/Api/Experimental/Tx.hs	Adds evaluateSignedTx wrapper and re-exports new symbols under a "Transaction evaluation" section.
cardano-api/src/Cardano/Api/Experimental.hs	Re-exports new evaluation API under a new sub-section.
cardano-api/test/cardano-api-test/Test/Cardano/Api/Experimental/Fee.hs	Three new property tests for the new evaluation function.
cardano-rpc/src/Cardano/Rpc/Server/Internal/UtxoRpc/Eval.hs	Refactor: replace inlined pipeline with a call to Exp.evaluateTransaction.
.changes/20260515_cardano_api_evaluate_transaction.yml	Herald changelog fragment (feature) for cardano-api.
.changes/20260515_cardano_rpc_use_evaluate_transaction.yml	Herald changelog fragment (refactoring) for cardano-rpc.