feat(app): float composer trackers as pills over the transcript (#3482)

The subagents track and the task list were stacked cards above the
composer. Each one pushed the composer further down the pane and painted
an opaque band the timeline stopped at, and both spent a full row on a
count that fits in a pill.

Both are now pills that open a panel — a popover on wide screens, a sheet
on compact ones, from the existing menu engine rather than a fourth
floating-panel implementation. The row frame is shared, so a subagent row
and a task row sit on the same rail whatever their contents.

The bar mounts inside the transcript's animated container and pins itself
to the bottom edge, so scrolled content passes under the pills instead of
stopping above them. It stays a child of that container rather than a
sibling floating over the composer: on Android a view outside its parent's
bounds paints but takes no touches, and every pill is pressable. The
container carries the same keyboard transform the composer does, so the
pills track the composer's top edge when the keyboard moves.

The tracker state moves out of the composer with it. None of it was
composer state; it lived there because that is where it used to render.

packages/app/src/i18n/resources/ja.ts

@@ -339,7 +339,6 @@ export const ja: TranslationResources = {
       title: "タスク",
       empty: "タスクがまだありません。",
       tasksProgress: "{{completed}}/{{total}}タスク",
-      tasksProgressCurrent: "{{completed}}/{{total}}タスク · {{task}}",
       activity: {
         created: "{{count}}件のタスクを作成",
         added: "追加",
@@ -1636,12 +1635,14 @@ export const ja: TranslationResources = {
     backdrop: "メニューの背景",
   },
   subagents: {
+    title: "サブエージェント",
+    pillLabelOne: "サブエージェント 1 件",
+    pillLabelMany: "サブエージェント {{count}} 件",
     detachAction: "{{label}}を切り離す",
     detachTooltip: "サブエージェントを切り離す",
     archiveAction: "{{label}}をアーカイブ",
     archiveTooltip: "サブエージェントをアーカイブ",
     archiveFinishedAction: "完了したサブエージェントをアーカイブ",
-    archiveFinishedTooltip: "完了した項目をアーカイブ",
     archiveFinishedRetry: "再試行 ({{failed}}/{{total}})",
   },
   panels: {