Implement linear task chains and recurring maintenance buckets

Backend, web timeline, and Android widget wiring for the last two
unimplemented items from doot-future-task-scheduling-ideas.

Chains: task_chains table + chain_id/chain_position/chain_unlocked on
native_tasks (migration 026), WIP-limit-1 advancement hooked into
CompleteNativeTask, locked tasks excluded from all date-based queries,
5 new /api/widget/chains* endpoints, an N/M position badge on web and
Android widget rows.

Buckets: maintenance_buckets table + bucket_id/bucket_state/
bucket_last_active_at on native_tasks (migration 027),
staleness-then-priority selection scoring, a new RunBucketCycleCheck
scheduler loop, 5 new endpoints including the distinct Defer action, a
Defer button on web and Android widget rows.

Also corrected stale "not yet approved" status headers on the two
already-shipped specs this work depended on (labels/projects, budgets/
availability) -- their headers were never updated after implementation.

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

1 files changed, 165 insertions, 0 deletions

diff --git a/internal/store/chains_test.go b/internal/store/chains_test.go
new file mode 100644
index 0000000..6d3e450
--- /dev/null
+++ b/internal/store/chains_test.go
@@ -0,0 +1,165 @@
+package store
+
+import (
+	"testing"
+)
+
+func TestCreateChain_SeedsPositionsCorrectly(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+
+	chain, err := s.CreateChain("Ham Radio Track", []string{"Study Technician", "Pass Technician exam", "Study General"})
+	if err != nil {
+		t.Fatalf("CreateChain: %v", err)
+	}
+	if chain.Status != "active" {
+		t.Errorf("chain.Status = %q, want active", chain.Status)
+	}
+
+	tasks, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatalf("GetChainTasks: %v", err)
+	}
+	if len(tasks) != 3 {
+		t.Fatalf("len(tasks) = %d, want 3", len(tasks))
+	}
+	if !tasks[0].ChainUnlocked || tasks[0].DueDate == nil {
+		t.Errorf("position 0: ChainUnlocked=%v DueDate=%v, want unlocked with a due date", tasks[0].ChainUnlocked, tasks[0].DueDate)
+	}
+	for i := 1; i < 3; i++ {
+		if tasks[i].ChainUnlocked || tasks[i].DueDate != nil {
+			t.Errorf("position %d: ChainUnlocked=%v DueDate=%v, want locked with no due date", i, tasks[i].ChainUnlocked, tasks[i].DueDate)
+		}
+	}
+	if tasks[0].Content != "Study Technician" || tasks[1].Content != "Pass Technician exam" || tasks[2].Content != "Study General" {
+		t.Errorf("unexpected content order: %q, %q, %q", tasks[0].Content, tasks[1].Content, tasks[2].Content)
+	}
+}
+
+func TestCompleteNativeTask_AdvancesChain(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+
+	chain, err := s.CreateChain("Track", []string{"Step 1", "Step 2"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	tasks, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := s.CompleteNativeTask(tasks[0].ID); err != nil {
+		t.Fatalf("CompleteNativeTask: %v", err)
+	}
+
+	after, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !after[1].ChainUnlocked || after[1].DueDate == nil {
+		t.Errorf("position 1 after completing position 0: ChainUnlocked=%v DueDate=%v, want unlocked with a due date", after[1].ChainUnlocked, after[1].DueDate)
+	}
+
+	updatedChain, err := s.GetChain(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if updatedChain.Status != "active" {
+		t.Errorf("chain.Status = %q, want active (not yet done)", updatedChain.Status)
+	}
+}
+
+func TestCompleteNativeTask_LastPosition_MarksChainCompleted(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+
+	chain, err := s.CreateChain("Track", []string{"Only step"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	tasks, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := s.CompleteNativeTask(tasks[0].ID); err != nil {
+		t.Fatalf("CompleteNativeTask: %v", err)
+	}
+
+	updatedChain, err := s.GetChain(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if updatedChain.Status != "completed" {
+		t.Errorf("chain.Status = %q, want completed", updatedChain.Status)
+	}
+}
+
+func TestCompleteNativeTask_PausedChain_DoesNotAdvance(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+
+	chain, err := s.CreateChain("Track", []string{"Step 1", "Step 2"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.SetChainStatus(chain.ID, "paused"); err != nil {
+		t.Fatal(err)
+	}
+	tasks, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if err := s.CompleteNativeTask(tasks[0].ID); err != nil {
+		t.Fatalf("CompleteNativeTask: %v", err)
+	}
+
+	after, err := s.GetChainTasks(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if after[1].ChainUnlocked {
+		t.Error("position 1 should still be locked while chain is paused")
+	}
+
+	// Resuming re-enables advancement on the *next* completion.
+	if err := s.SetChainStatus(chain.ID, "active"); err != nil {
+		t.Fatal(err)
+	}
+	if err := s.CompleteNativeTask(tasks[1].ID); err != nil {
+		t.Fatalf("CompleteNativeTask after resume: %v", err)
+	}
+	updatedChain, err := s.GetChain(chain.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if updatedChain.Status != "completed" {
+		t.Errorf("chain.Status = %q, want completed after resuming and finishing the last step", updatedChain.Status)
+	}
+}
+
+func TestGetUndatedNativeTasks_ExcludesLockedChainTasks(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+
+	chain, err := s.CreateChain("Track", []string{"Step 1", "Step 2", "Step 3"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	_ = chain
+
+	undated, err := s.GetUndatedNativeTasks()
+	if err != nil {
+		t.Fatalf("GetUndatedNativeTasks: %v", err)
+	}
+	for _, task := range undated {
+		if task.ChainID != "" && !task.ChainUnlocked {
+			t.Errorf("locked chain task %q leaked into GetUndatedNativeTasks", task.ID)
+		}
+	}
+}
+
+func TestGetChain_UnknownID_ReturnsErrNotFound(t *testing.T) {
+	s := newNativeTasksTestStore(t)
+
+	if _, err := s.GetChain("does-not-exist"); err != ErrNativeTaskNotFound {
+		t.Errorf("err = %v, want ErrNativeTaskNotFound", err)
+	}
+}