Publish 1.0 deprecation kill-list ADR

[AustinKelsay]

Part of #154
Blocked by: none

Goal

Add ADR 0003 documenting planned Public Facade consolidations and Compatibility Alias removals for the next major release, and add a CHANGELOG Unreleased note that points maintainers at that kill-list without removing anything in 0.x.

Acceptance

• docs/adr/0003-*.md exists and lists each planned removal with replacement.
• CHANGELOG Unreleased mentions the planned-major kill-list (docs-only; no removals).
• CONTEXT Public Facade / Compatibility Alias terms remain accurate.

Notes

AFK. Documentation only. ADR 0002 logger aliases stay until major.

[AustinKelsay]

Implemented on feature/cleanup-tier-ab-api-surface and included in PR #163 targeting staging. Spec #154.