fix: issue #20 cmd-J panel tab strip visibility and output panel parity

lib/bds/ui/task_grouping.ex

@@ -0,0 +1,91 @@
+defmodule BDS.UI.TaskGrouping do
+  @moduledoc """
+  Groups task snapshot entries for the bottom panel's Tasks tab, mirroring the
+  old app's `taskGrouping.ts`: tasks sharing a `group_id` collapse into one
+  group entry (ordered by first appearance), everything else stays a single
+  entry. Groups summarize to per-status counts plus an aggregate progress in
+  the 0.0..1.0 range.
+  """
+
+  @type task :: map()
+  @type entry :: {:single, task()} | {:group, String.t(), String.t(), [task()]}
+  @type summary :: %{
+          total: non_neg_integer(),
+          running: non_neg_integer(),
+          pending: non_neg_integer(),
+          completed: non_neg_integer(),
+          failed: non_neg_integer(),
+          cancelled: non_neg_integer(),
+          progress: float()
+        }
+
+  @spec build_task_entries([task()]) :: [entry()]
+  def build_task_entries(tasks) when is_list(tasks) do
+    {singles, groups} =
+      tasks
+      |> Enum.with_index()
+      |> Enum.reduce({[], %{}}, fn {task, index}, {singles, groups} ->
+        case Map.get(task, :group_id) do
+          nil ->
+            {[{index, task} | singles], groups}
+
+          group_id ->
+            groups =
+              Map.update(groups, group_id, {index, Map.get(task, :group_name) || group_id, [task]}, fn {first_index, name, grouped} ->
+                {first_index, name, [task | grouped]}
+              end)
+
+            {singles, groups}
+        end
+      end)
+
+    single_entries = Enum.map(singles, fn {index, task} -> {index, {:single, task}} end)
+
+    group_entries =
+      Enum.map(groups, fn {group_id, {index, name, grouped}} ->
+        {index, {:group, group_id, name, Enum.reverse(grouped)}}
+      end)
+
+    (single_entries ++ group_entries)
+    |> Enum.sort_by(fn {index, _entry} -> index end)
+    |> Enum.map(fn {_index, entry} -> entry end)
+  end
+
+  @spec summarize_task_group([task()]) :: summary()
+  def summarize_task_group(tasks) when is_list(tasks) do
+    base = %{total: 0, running: 0, pending: 0, completed: 0, failed: 0, cancelled: 0, progress: 0.0}
+
+    summary =
+      Enum.reduce(tasks, base, fn task, acc ->
+        status = Map.get(task, :status)
+
+        acc
+        |> Map.update!(:total, &(&1 + 1))
+        |> count_status(status)
+        |> Map.update!(:progress, &(&1 + progress_contribution(task)))
+      end)
+
+    if summary.total > 0 do
+      %{summary | progress: summary.progress / summary.total}
+    else
+      summary
+    end
+  end
+
+  defp count_status(acc, status) when status in [:running, :pending, :completed, :failed, :cancelled],
+    do: Map.update!(acc, status, &(&1 + 1))
+
+  defp count_status(acc, _status), do: acc
+
+  # Finished tasks count as fully done no matter their outcome, pending tasks
+  # contribute nothing yet (old-app getProgressContribution).
+  defp progress_contribution(%{status: status}) when status in [:completed, :failed, :cancelled],
+    do: 1.0
+
+  defp progress_contribution(%{status: :pending}), do: 0.0
+
+  defp progress_contribution(%{progress: progress}) when is_number(progress),
+    do: progress |> max(0.0) |> min(1.0)
+
+  defp progress_contribution(_task), do: 0.0
+end