Decide whether a report shows that steps were spliced in from another oath

[aslakhellesoy]

Follow-up to #104 (ADR 0016), open question 3.

A spliced section's steps are flattened into the referencing example. Nothing in a test report says reuse happened — the referencing example lists the steps as if they were written in place, and the consumed oath shows as one bookkeeping test (vitest) or nothing at all (every other adapter).

Whether that is right depends on what a reader of CI output should be able to tell:

• Flat (today). The example reads as its steps, wherever they came from. Simplest, and arguably honest: the steps did run, in that order, in that example.
• Nested. The spliced steps appear under a describe-like group named for the section. Makes reuse visible; costs a level of nesting in every adapter's report shape, and the seven adapters do not share one.
• Invisible but attributed. Flat, but each step carries where it came from — which is what docPath already is, once Run results: carry per-step document identity so a failure inside a referenced section lands in the editor #105 lands and the payload carries it.

The third probably falls out of #105 for free, and may be all that's wanted. Worth deciding before anyone builds nesting.

[aslakhellesoy]

Resolved by #113 (merged as d5fde84): see the ADR 0016 section "Open questions, and how each was decided" and reference/examples.mdx for the decision as documented.