feat: search --hop walks FROM_FILE to Person. (#30)

Parser no longer errors; hop 1 returns File, hop 3 reaches Person.
Rebuild writes Leaf-[:FROM_FILE]->File so the walk is not empty
on a fresh index (Gitea #17).

internal/brain/rank/query.go

@@ -7,3 +7,30 @@ const FTSStmt = "CALL QUERY_FTS_INDEX('Leaf', 'id', $q) " +
 
 const VecStmt = "CALL QUERY_VECTOR_INDEX('Leaf', 'Leaf_vec', $q, $n) " +
 	"RETURN node.id, node.text, node.root, node.source, distance ORDER BY distance LIMIT $n"
+
+// HopStmt is the Cypher walk from a search hit. Depth 1 = File, 2 = Commit, 3 = Person.
+func HopStmt(depth int) string {
+	switch depth {
+	case 1:
+		return "MATCH (l:Leaf {id:$id})-[:FROM_FILE]->(f:File) RETURN f.id, f.path, 1"
+	case 2:
+		return "MATCH (l:Leaf {id:$id})-[:FROM_FILE]->(f:File)-[:HAS_VERSION]->(c:Commit) RETURN c.id, c.subject, 2"
+	case 3:
+		return "MATCH (l:Leaf {id:$id})-[:FROM_FILE]->(f:File)-[:HAS_VERSION]->(c:Commit)-[:AUTHORED]->(p:Person) RETURN p.id, p.name, 3"
+	default:
+		return ""
+	}
+}
+
+func HopLabel(depth int) string {
+	switch depth {
+	case 1:
+		return "File"
+	case 2:
+		return "Commit"
+	case 3:
+		return "Person"
+	default:
+		return ""
+	}
+}