chore: add gitignore for mock-seed, roam CI workflow, formatting

- Add tools/mock-seed/ to .gitignore
- Add .github/workflows/roam.yml CI workflow
- Add .roam/fitness.yaml architectural fitness rules
- Rustfmt formatting fixes in show.rs and vector.rs
- Beads sync

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/search/vector.rs

@@ -150,7 +150,10 @@ mod tests {
     #[test]
     fn test_knn_k_reproduces_original_bug_scenario() {
         let k = compute_knn_k(1500, 1);
-        assert!(k <= SQLITE_VEC_KNN_MAX, "k={k} exceeded 4096 at RECALL_CAP with 1 chunk");
+        assert!(
+            k <= SQLITE_VEC_KNN_MAX,
+            "k={k} exceeded 4096 at RECALL_CAP with 1 chunk"
+        );
     }
 
     #[test]