Rework Tasks tab: Chains section, checklist modal, project visibility

The flat Tasks-tab atom list was silently dumping every chain step
(locked and unlocked) and dormant bucket-pool items in as ordinary
undated cards, with no chain/project context and no protection against
completing a locked step out of order.

- CompleteNativeTask now rejects completing a locked chain task
  (ErrChainTaskLocked), mapped to 400 in both the widget and web
  complete-atom handlers.
- Chain tasks and dormant bucket items are excluded from the flat atom
  list; a new "Chains" section shows one card per active/paused chain
  with the current step and N/M progress.
- New chain checklist modal (GET /chains/{id}) lists every position in
  order with pause/resume/abandon -- the web view originally deferred
  as Android-only.
- Fixed a real bug this surfaced: resuming a paused chain only flipped
  the status flag, never unlocking the deferred successor, so a chain
  paused right after a completion stayed stuck forever. SetChainStatus
  now catches up the deferred advancement on resume, idempotently.
- Atom cards gained a project-name chip for general visibility.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EZ7ikw2ukGJFTHE3bJS7zL

1 files changed, 53 insertions, 0 deletions

diff --git a/internal/handlers/atoms_test.go b/internal/handlers/atoms_test.go
index 521b147..7cb94a7 100644
--- a/internal/handlers/atoms_test.go
+++ b/internal/handlers/atoms_test.go
@@ -44,6 +44,59 @@ func TestBuildUnifiedAtomList_WithNativeTasks(t *testing.T) {
 	}
 }
 
+func TestBuildUnifiedAtomList_ExcludesLockedChainTasks(t *testing.T) {
+	s, err := store.New(":memory:", "../../migrations")
+	if err != nil {
+		t.Fatalf("failed to create in-memory store: %v", err)
+	}
+	defer s.Close()
+
+	if _, err := s.CreateChain("Track", []models.ChainTaskInput{
+		{Content: "Step 1"}, {Content: "Step 2"}, {Content: "Step 3"},
+	}); err != nil {
+		t.Fatal(err)
+	}
+
+	atoms, _, err := BuildUnifiedAtomList(s, nil)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	for _, a := range atoms {
+		if a.Title == "Step 1" || a.Title == "Step 2" || a.Title == "Step 3" {
+			t.Errorf("chain task %q should not appear in the flat atom list (chains get their own Chains section)", a.Title)
+		}
+	}
+}
+
+func TestBuildUnifiedAtomList_ExcludesDormantBucketItems(t *testing.T) {
+	s, err := store.New(":memory:", "../../migrations")
+	if err != nil {
+		t.Fatalf("failed to create in-memory store: %v", err)
+	}
+	defer s.Close()
+
+	bucket, err := s.CreateBucket("Gutters", 30, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.CreateNativeTask(models.Task{ID: "pool-item", Content: "Clean gutters", Priority: 1}); err != nil {
+		t.Fatal(err)
+	}
+	if err := s.AddBucketItem(bucket.ID, "pool-item"); err != nil {
+		t.Fatal(err)
+	}
+
+	atoms, _, err := BuildUnifiedAtomList(s, nil)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	for _, a := range atoms {
+		if a.Title == "Clean gutters" {
+			t.Error("dormant bucket-pool item should not appear in the flat atom list")
+		}
+	}
+}
+
 func TestBuildUnifiedAtomList_WithClaudomator(t *testing.T) {
 	s, err := store.New(":memory:", "../../migrations")
 	if err != nil {