#165 Make ADR import report malformed files without blocking preview

[Anonymous]

Originally created by: TheoV823

Track ADR import behavior when malformed ADR files are present.

Dry-run preview should report parse errors while still showing valid ADRs, precedence outcomes, and existing-memory collisions.

Apply should refuse to write until parse errors are fixed.

Scope: CLI, ADR import flow, validation, and regression tests only. Do not change DecisionRetriever, runtime enforcement semantics, or ADR precedence rules.