Honor explicit follow-up questions after a submitted work choice

Why: A fresh question referencing an earlier result could be mistaken for a duplicate background request.

Evidence: The new English-summary reference regression failed with the old receipt branch and passes with the explicit-reference distinction.

Impact: Deduplicate inferred pending choices while allowing explicit new requests to use the saved result.

Refs: feature/workbench-flow-completion review P1

internal/runmgr/workcard.go

@@ -292,6 +292,7 @@ func materialPurposeRequest(text string) bool {
 }
 
 func (m *Manager) bindWorkContext(conv core.Conversation, msg core.Message, ref *WorkReference, runIDs ...core.ID) (string, error) {
+	inferred := ref == nil
 	if ref == nil {
 		ref = m.directWorkReference(conv, messageText(msg))
 	}
@@ -304,7 +305,7 @@ func (m *Manager) bindWorkContext(conv core.Conversation, msg core.Message, ref
 			return "", err
 		}
 		if d := card.Work.Decision; d != nil && materialPurposeRequest(messageText(msg)) {
-			if d.State == "dispatching" || d.State == "submitted" {
+			if inferred && (d.State == "dispatching" || d.State == "submitted") {
 				return workReceiptPrefix + card.ID, nil
 			}
 			if d.State == "open" || d.State == "deferred" {

internal/runmgr/workcard_test.go

@@ -169,6 +169,24 @@ func TestDirectMaterialSummaryUsesExistingForegroundOnly(t *testing.T) {
 	}
 }
 
+func TestExplicitWorkReferenceAllowsNewSummaryAfterPreviousChoice(t *testing.T) {
+	c, card := completedMaterialWork(t)
+	_, err := c.mgr.WorkCardAction(c.run.Owner, card.ID, "work.submit", core.WorkCardAction{ResultVersion: 1, SelectedIDs: []string{"summary"}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	waitBackgroundIdle(t, c)
+	conv, err := c.mgr.st.GetConversation(c.run.Owner, c.run.ConversationID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	msg := core.Message{Parts: []core.Part{{Type: core.PartText, Text: "请把这份材料的重点总结为英文"}}}
+	context, err := c.mgr.bindWorkContext(conv, msg, &WorkReference{card.ID, 1})
+	if err != nil || strings.HasPrefix(context, workReceiptPrefix) || !strings.Contains(context, card.Work.Result) {
+		t.Fatalf("explicit follow-up request discarded: %q %v", context, err)
+	}
+}
+
 func TestButtonAndDirectSummaryRaceKeepsOneExecution(t *testing.T) {
 	c, card := completedMaterialWork(t)
 	hold := &holdRunner{release: make(chan struct{})}