Entity preview mutation safety

Entity mutation APIs are preview-only by default and require ?apply=true; CLI dedup applies only with --yes. Chose read-only preview over eagerly resolving state because ensureProject() or lazy remote reconciliation can create rows during an alleged dry run. Preview stays non-mutating and non-interactive even with --yes or --interactive; only apply mode may ensure projects. Destructive CLI operations require --yes, --json --interactive is invalid, and core merge rejects incompatible types before BEGIN IMMEDIATE.