research: decide telemetry v2 versus ADR-0056 delivery (X7)

[pacphi]

Why

ADR-0056's schema version 2 collides with v4's telemetry contract v2, before the GA freeze (v5 review X7).

In scope

Choose: delivery becomes v3 after GA; v2 reserves a delivery: unavailable section; or v2 defines an extension map. Record it in ADR-0064 or ADR-0054.

Out of scope

Implementing delivery metrics.

Acceptance criteria

• Maintainer decision recorded before feat: telemetry contract v2 #375 starts

Dependencies

Blocked by: None

Blocks: #375, #387

Plan

• Release: 4.0.0-beta.3
• Size: size:S · Workstream: ws:project-scope
• Epic: feat: project-scope P6, the dashboard for all work (epic) #301
• Card: P6-07 in the card inventory
• Sources: v5 impact review (docs(plans): v4 GA master plan, supersession ledger and v5 registers #290) X7

Verification

Each acceptance criterion is checked on the pull request.