feat: Phase 9 gaps closed — ApprovalService.Decide convergence, execlog fold, execworker poller

- ApprovalService (core/app/approval.go) + ApprovalRepo (postgres adapter) with
  full decide transaction: HMAC token verify, approval flip, execution un-gate,
  session-scoped window keys (+session suffix matching GovernanceStore gate),
  nomos session flip, audit+event on failure abort. httpapi DecideApproval now
  a thin presenter delegating to the service. ListPending payload format fixed
  (json.Unmarshal not raw-wrap).
- execlog folded into postgres adapter: internal/execlog deleted, NewExecutionLog
  / ReadExecutionLog live in the db package, callers updated (mcp, httpapi).
- execworker poller over ExecutionService.DispatchQueued: advisory lock leak
  fixed (defer/recover per execution), correlation_id preserved via Finalize
  event emission (ExecRunRepo.Finalize now emits execution.{status} with
  correlation_id from the row).
- Phase 8 session export-rename completed: Store, New, and all 53 methods
  exported; cmd/nomos/ agent.go fixed to use session.PendingContinuation etc.
- Coverage gates: ExecutionService.Submit 93.1%, PolicyService.Decide 100%.
- Plans index updated, VERSION bumped to 0.36.0.

cmd/nomos/server.go

@@ -17,6 +17,7 @@ import (
 	"github.com/dtoro/oikos/internal/nomos/session"
 	"github.com/dtoro/oikos/internal/safego"
 	"github.com/dtoro/oikos/internal/secrets"
+	"github.com/jackc/pgx/v5"
 )
 
 func main() {
@@ -425,7 +426,7 @@ func handleSessionsList(w http.ResponseWriter, r *http.Request, st *session.Stor
 			limit = n
 		}
 	}
-	sessions, err := st.ListSessionsFiltered(r.Context(), ListFilter{
+	sessions, err := st.ListSessionsFiltered(r.Context(), session.ListFilter{
 		Outcome:  q.Get("outcome"),
 		Status:   q.Get("status"),
 		EntityID: q.Get("entity_id"),
@@ -692,4 +693,4 @@ func truncate(s string, n int) string {
 		return s
 	}
 	return s[:n] + "..."
-}
+}