Part of #2930. P02, patterned; owner ac-dev-rust-v4; depends on P01 merged to main with verified ancestry. Clean and empty-title room creation currently persist placeholder prose. Persist an empty body while keeping title, BOM/EOL, transaction/recovery, topic/status and USER-title behavior.

Files: src-tauri/src/cli/task_ops.rs, src-tauri/src/commands/entity_creation.rs, src-tauri/src/commands/ac_discovery.rs.

Acceptance: creation yields UTF8 LF 23-byte Clean frontmatter without body; Clean removes body explicitly; repeated Clean is NoOp including BOM/CRLF; backups/failure recovery preserved; first append after Clean has no placeholder; existing human/legacy bodies remain intact outside explicit Clean; watcher null/revision contract retained.

Validation from repo root: cargo test --locked --manifest-path src-tauri/Cargo.toml cli::task_ops::tests; filters prepare_new_room_task_content/build_task_content/snapshot_facade_is_cli_dto_with_only_root_normalization/poll_partial_only_and_clean_seed_deliver_explicit_null_with_new_revision; cargo fmt --all -- --check; relevant layering tests, UI regression and exact-head CI per canonical plan.

Canonical specification: D:/0_repos/AgentsCommander_iac/.ac/plans/2930-empty-task-description/P02-v3-rust-empty-defaults.md. Phase-SHA256 717F99B2264ADB28CC3FB571752D77B31F761497E1EB83B001762F9940E074DC. No migration or I2931 changes. Human approval of exact set pending; no implementation authorized yet.