fix(sessions): use entities query for list — hybridSearch requires project arg

hybridSearch mandates a project scope, but sessions scatter across
per-session projects (session-<uuid>). The entities query accepts
optional project — omit it to list SESSION entities across all projects.

Also adds projectId to the list response so callers can scope follow-up
queries to the right session project.

Fixes: GET X-Service:sessions X-Resource:sessions returning 502

internal/sessions/handler.go

@@ -180,9 +180,12 @@ func (h *Handler) handleList(w http.ResponseWriter, r *http.Request) {
 		searchQuery = fmt.Sprintf("%s cwd:%s", searchQuery, cwd)
 	}
 
+	// entities query (not hybridSearch) — project arg is optional, so it queries
+	// across ALL projects. Required because each session lives in its own
+	// session-<uuid> project; there is no single project to hybridSearch against.
 	gqlQuery := `query($q:String!,$limit:Int!){
-		hybridSearch(query:$q,limit:$limit,entityType:SESSION){
-			entities{id name summary tCreated}
+		entities(query:$q,limit:$limit,entityType:SESSION){
+			entities{id name summary projectId tCreated}
 			searchMode
 		}
 	}`