recover: restore untracked work from recovery branch (no Gemini changes)

Recovered files with no Claude→Agent contamination:
- docs/adr/002-task-state-machine.md
- internal/api/logs.go/logs_test.go: task-level log streaming endpoint
- internal/api/validate.go/validate_test.go: POST /api/tasks/validate
- internal/api/server_test.go, storage/db_test.go: expanded test coverage
- scripts/reset-failed-tasks, reset-running-tasks
- web/app.js, index.html, style.css: frontend improvements
- web/test/: active-tasks-tab, delete-button, filter-tabs, sort-tasks tests

Manually applied from server.go diff (skipping Claude→Agent rename):
- taskLogStore field + validateCmdPath field
- DELETE /api/tasks/{id} route + handleDeleteTask
- GET /api/tasks/{id}/logs/stream route
- POST /api/tasks/{id}/resume route + handleResumeTimedOutTask
- handleCancelTask: allow cancelling PENDING/QUEUED tasks directly

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 58 insertions, 0 deletions

diff --git a/internal/storage/db_test.go b/internal/storage/db_test.go
index 395574c..fcdc529 100644
--- a/internal/storage/db_test.go
+++ b/internal/storage/db_test.go
@@ -473,6 +473,64 @@ func TestStorage_UpdateTaskQuestion(t *testing.T) {
 	}
 }
 
+func TestDeleteTask_RemovesTaskAndExecutions(t *testing.T) {
+	db := testDB(t)
+	now := time.Now().UTC()
+	db.CreateTask(makeTestTask("del-task", now))
+	db.CreateExecution(&Execution{ID: "del-exec-1", TaskID: "del-task", StartTime: now, Status: "COMPLETED"})
+	db.CreateExecution(&Execution{ID: "del-exec-2", TaskID: "del-task", StartTime: now.Add(time.Minute), Status: "COMPLETED"})
+
+	if err := db.DeleteTask("del-task"); err != nil {
+		t.Fatalf("DeleteTask: %v", err)
+	}
+
+	_, err := db.GetTask("del-task")
+	if err == nil {
+		t.Error("expected error getting deleted task, got nil")
+	}
+
+	execs, err := db.ListExecutions("del-task")
+	if err != nil {
+		t.Fatalf("ListExecutions: %v", err)
+	}
+	if len(execs) != 0 {
+		t.Errorf("want 0 executions after delete, got %d", len(execs))
+	}
+}
+
+func TestDeleteTask_CascadesSubtasks(t *testing.T) {
+	db := testDB(t)
+	now := time.Now().UTC()
+
+	parent := makeTestTask("parent-del", now)
+	child := makeTestTask("child-del", now)
+	child.ParentTaskID = "parent-del"
+
+	db.CreateTask(parent)
+	db.CreateTask(child)
+
+	if err := db.DeleteTask("parent-del"); err != nil {
+		t.Fatalf("DeleteTask: %v", err)
+	}
+
+	_, err := db.GetTask("parent-del")
+	if err == nil {
+		t.Error("parent should be deleted")
+	}
+	_, err = db.GetTask("child-del")
+	if err == nil {
+		t.Error("child should be deleted when parent is deleted")
+	}
+}
+
+func TestDeleteTask_NotFound(t *testing.T) {
+	db := testDB(t)
+	err := db.DeleteTask("nonexistent")
+	if err == nil {
+		t.Fatal("expected error for nonexistent task, got nil")
+	}
+}
+
 func TestStorage_GetLatestExecution(t *testing.T) {
 	db := testDB(t)
 	now := time.Now().UTC()