PR #684 — Milestone 1: Transaction Trace CLI

[github-actions]

Parent: #730
PR: #684

Estimated Delivery: 4 weeks from start

Estimated Effort: 8 engineer-weeks

Focus: One useful command to inspect successful transactions.

Deliverables / Value Metrics:

• dpm trace <update-id> plugin command.
• Support for local and remote participant JSON Ledger API endpoints.
• Support for --submitter, --read-as, and bearer-token based access through token files, direct token arguments, or environment variables.
• Human-readable transaction tree for successful transactions.
• Create, exercise, archive, and reassignment event rendering.
• Contract ids, parties, witnesses, signatories, observers, choice arguments, return values, and payloads where visible.
• Participant-visible projection labeling.
• Documentation with a local Canton example and an authorized remote participant example.

Acceptance Criteria:

• A developer can run dpm trace <update-id> --submitter <url> --read-as <party> against a local Canton participant and inspect a successful transaction.
• The same command shape works against an authorized remote participant endpoint.
• The CLI renders a readable transaction tree for create, exercise, archive, and reassignment events where present.
• Output labels the result as a participant-visible projection and does not imply access to non-visible private data.
• At least three representative Daml examples are included: create, exercise with child create, and archive/consuming exercise.