docs: constrain ADR skill workflow

[dapi]

What changed

• restrict adr-writing usage to its MADR / E.C.A.D.R. quality checklist and review heuristics;
• make the repository-local ADR path, naming, frontmatter, and lifecycle rules explicitly authoritative;
• align template_target_path and feature-template ADR placeholders with ADR-XXX-short-decision-name.md;
• synchronize the template, installed Memory Bank copy, and ownership lock.

Why

The generic adr-writing workflow requires docs/adrs/NNNN-*.md and a different metadata/status model. Following it unconditionally could create ADRs outside memory-bank/adr/ and violate the repository’s governed ADR contract.

Impact

Agents can still reuse the skill’s quality criteria, while ADR creation and review remain compatible with the Memory Bank structure and lifecycle.

Validation

• memory-bank-cli lint --scope-root template/memory-bank --entrypoint template/memory-bank/README.md
• memory-bank-cli lint --scope-root memory-bank --entrypoint memory-bank/README.md
• memory-bank-cli doctor --profile template
• memory-bank-cli doctor
• git diff --check
• independent Codex review