Extract 2119-line monolithic atlas.rs into 8 focused modules under src/bin/atlas/: main.rs (thin dispatch), common.rs (shared types and DB helpers), show.rs, mutate.rs, stats.rs, systems.rs, author.rs, and sync_wiki.rs. Commands enum stays in main.rs; each match arm delegates to module::cmd_fn(&conn, args). No behavior change. Closes #776. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>