fix(indexer): use incremental contract cleanup on untrack

internal/indexer/multi.go

@@ -3203,6 +3203,10 @@ func (mi *MultiIndexer) UntrackRepo(repoPrefix string) (int, int) {
 		mi.mu.Unlock()
 		return 0, 0
 	}
+	// Snapshot the exact derived-contract frontier before deleting the repo.
+	// Cross-repo bridge nodes can be owned by a surviving repo, so purge alone
+	// cannot remove every dangling derived edge.
+	contractPlan := mi.contractInvalidationPlanForRepo(idx)
 	delete(mi.repos, repoPrefix)
 	delete(mi.indexers, repoPrefix)
 	mi.mu.Unlock()
@@ -3266,7 +3270,9 @@ func (mi *MultiIndexer) UntrackRepo(repoPrefix string) (int, int) {
 		}
 	}
 
-	mi.ReconcileContractEdges()
+	if !contractPlan.Empty() {
+		mi.ReconcileContractEdgesForFrontier(contractPlan)
+	}
 
 	// Keep the closed slot installed until every purge/config side effect is
 	// complete, then remove only the exact generation drained above. A stale

internal/indexer/untrack_contract_frontier.go

@@ -0,0 +1,50 @@
+package indexer
+
+import "github.com/zzet/gortex/internal/graph"
+
+// contractInvalidationPlanForRepo snapshots the derived contract frontier
+// before the repository registry and graph nodes are removed. Cross-repository
+// bridge edges may be owned by a surviving repository, so the removed contract
+// IDs alone are not enough; include every bridge that points at them.
+func (mi *MultiIndexer) contractInvalidationPlanForRepo(idx *Indexer) DerivedInvalidationPlan {
+	var plan DerivedInvalidationPlan
+	if idx == nil {
+		return plan
+	}
+
+	registry := idx.ContractRegistry()
+	if registry == nil {
+		return plan
+	}
+
+	contractIDs := make(map[string]struct{})
+	for _, contract := range registry.All() {
+		if contract.ID == "" {
+			continue
+		}
+		plan.ContractGroups = append(plan.ContractGroups, ContractGroupFrontier{
+			WorkspaceID: contract.EffectiveWorkspace(),
+			ProjectID:   contract.EffectiveProject(),
+			ContractID:  contract.ID,
+		})
+		if contract.SymbolID != "" {
+			plan.ContractSymbolIDs = append(plan.ContractSymbolIDs, contract.SymbolID)
+		}
+		contractIDs[contract.ID] = struct{}{}
+	}
+	if len(contractIDs) == 0 {
+		return plan
+	}
+
+	incoming := mi.graph.GetInEdgesByNodeIDs(sortedStringKeys(contractIDs))
+	bridgeIDs := make(map[string]struct{})
+	for _, edges := range incoming {
+		for _, edge := range edges {
+			if edge != nil && edge.Kind == graph.EdgeBridges && edge.From != "" {
+				bridgeIDs[edge.From] = struct{}{}
+			}
+		}
+	}
+	plan.ContractBridgeNodeIDs = sortedStringKeys(bridgeIDs)
+	return plan
+}