[feat] Tell a driver which payload fields next and report ignored #1164

Parent: #818

Goal

A driver learns from the response when the CLI did not use part of what it sent.

Problem

parseReport and driverFrom (src/workflow/engine.ts) copy only the fields they know, and drop the rest without notice. Two cases lose data without any signal:

• A typo, such as tokenz or sesion.
• Version skew: a driver that sends a field from a newer contract to an older CLI. For example, the pr_url from [feat] Add workflow workspaces, branches, and session continuation #1080 and [feat] Deliver workflow branches as pull requests #1090, or cancelled handling from [feat] Add bounded loops and parallel for_each #1079.

Contract

The success envelope of next and report gets an ignored list. It names each top-level payload field, and each driver.<field>, that this CLI does not read:

{ "data": { "accepted": true, "revision": 4, "step": { "id": "build", "status": "succeeded", "outcome": "success" },
  "ignored": ["tokenz", "driver.region"] } }

• Names only, never values, because an unknown field may hold anything.
• Left out when empty, so the envelope of today's drivers does not change.
• An error envelope stays as it is.
• The local driver prints ignored to stderr. It should never have any, so a non-empty list there is a bug.

Acceptance criteria

1. A report with "tokenz": {} is accepted and returns ignored: ["tokenz"]. The run state has no tokenz.
2. A next whose driver carries "region": "eu" returns ignored: ["driver.region"], and the lease still matches that driver.
3. A report with only known fields returns an envelope with no ignored key.
4. teamai workflow report <run> --json '<payload with an unknown field>' from the real CLI prints the field name in the envelope.

Test plan

• Unit tests on parseReport and parseDriverPayload.
• A conformance scenario in src/workflow/conformance.ts, because drivers see it (docs/dev/workflow-engine.md). Conformance compares with toMatchObject, so the other scenarios are unaffected.
• One real-CLI run for the PR body.

Watch out for

• The e2e tests workflow-inline and workflow-subworkflow compare whole done envelopes with toEqual. done must not gain the key when it is empty.
• Document ignored next to the outcome paragraph in docs/guide/workflow.md and its zh-CN page.

Dependencies

None.