Define multi-persona / multi-format roadmap (ADR-0002 + implementation plan)

[terisuke]

Meta-issue tracking the delivery of the ADR-0002 roadmap itself.

Scope

• Author ADR-0002 covering author persona × output format axes.
• Author the corresponding implementation plan with phase boundaries (A/B/C/D).
• Update ADR-0001 status, README, and issue-adr guardrails to reference the new ADR.
• File the 13 follow-up implementation issues that the ADR plans ([Phase A1] Refactor interview UI to chat-style transcript with editable past answers #17-[Phase D1] HTTP handler tests for internal/handlers/workflow.go #29).

This issue is a deliverable issue for the roadmap docs themselves. It is closed by the PR that lands ADR-0002 to develop. The 13 implementation issues remain open and are tracked in ADR 0002 — Tracked issues.

Acceptance criteria

• ADR-0002 merged into develop.
• Implementation plan merged into develop.
• ADR-0001 status updated to "extended by ADR-0002".
• README links to ADR-0002.
• All 13 phase issues filed with stable numbers and linked from the ADR.

[terisuke]

Roadmap docs have landed and the tracked implementation issues are now organized in ADR 0002, the implementation plan, and docs/implementation-plans/next-implementation-cut.md.

Current next target is #18, followed by #17, #20, #19, and #26. Closing this roadmap-delivery meta issue; the implementation issues remain open.