[palas]

Context

This PR is part of the effort to address: IntersectMBO/cardano-api#1382. The PR addresses the 5th checkbox of the 6th step: "Accept standalone signed and unsigned sub-transaction envelopes for inspection.".

Basically, we just add support for sub-transactions to transaction view. We do it both in --tx-file or --tx-body-file, the difference, as with top-transactions, is just that the list of signatures is not showed by --tx-body-file. Just for backwards compatibility, I think it would make sense to unify this.

How to trust this PR

Small change and follows the same behaviour as with top-transactions.

I would consider two things:

• Are we sure we want to use this command and not create a new sub-transaction view?
• Does readFileTxOrSubTx subsume readFileTxBody and readFileTx faithfully? I think it does

The PR also includes a golden file for a signed sub-transaction and an unsigned sub-transaction.

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/

[Copilot]

🟢 Approval recommended

No active review issues are reported for the changes adding standalone signed and unsigned sub-transaction viewing.

No open issues 🎉

What changed in this PR

Extends transaction view to inspect standalone signed and unsigned Dijkstra sub-transactions through the existing CLI, supporting the broader sub-transaction implementation effort.

Changes:

• Adds a shared reader for transaction and sub-transaction envelopes.
• Supports sub-transactions with both --tx-file and --tx-body-file, omitting witnesses for the latter.
• Adds signed and unsigned golden tests and a changelog entry.

File	Description
cardano-cli/​test/​cardano-cli-golden/​Test/​Golden/​Debug/​TransactionView.hs	Adds standalone signed and unsigned sub-transaction tests.
cardano-cli/​test/​cardano-cli-golden/​files/​golden/​dijkstra/​transaction-view-unsigned-sub-tx.yaml	Records expected unsigned output without witnesses.
cardano-cli/​test/​cardano-cli-golden/​files/​golden/​dijkstra/​transaction-view-signed-sub-tx.yaml	Records expected signed output with witnesses.
cardano-cli/​src/​Cardano/​CLI/​Read.hs	Adds the shared transaction/sub-transaction envelope reader.
cardano-cli/​src/​Cardano/​CLI/​EraIndependent/​Debug/​TransactionView/​Run.hs	Routes both input options to the appropriate renderer.
cardano-cli/​src/​Cardano/​CLI/​Compatible/​Json/​Friendly.hs	Exposes sub-transaction rendering for JSON and YAML output.
.changes/​20261104_173730_cardano-cli_pablo.lamela_view_sub_tx_files.yml	Documents the expanded input support.

_{Review effort: Balanced}