feat(client): workflow-graph Tasks page with teams board and jobs drawer

The Subagent page becomes the Tasks page per the approved Variant-D design:

- tasks-model.ts feeds BOTH modes from one pre-order node list: graph
  canvas (TasksGraph: layered nodes over bezier edges, drag-pan,
  wheel-zoom-to-cursor, phase frames, bottom-right control cluster) and
  the classic tree (TasksTree: keyboard navigable) — the view toggle and
  fold toggle stay reachable in both modes.
- Workflow runs (workflows.list) hang under their origin agent; member
  agents re-parent under the run node, missing ones synthesize from run
  data; completed leaf agents fold into per-parent aggregate nodes
  (click or cluster toggle to expand/re-collapse).
- Agent Teams (experimental): roster enriches nodes; a header chip opens
  the shared task board popover with basic CAS operations (complete /
  reopen / delete / reassign / create / edit); no experimental layer →
  the whole block hides (structural degradation).
- Background jobs move into a bottom drawer that auto-collapses at 8+
  agents (manual toggle wins); job output opens as an anchored popover
  (event replay, never the model's cursor); two-click kill preserved.
- Live activity lines render as glyph + tool + args (tool-icons map onto
  host primitive icons).
- Node click jumps to the transcript; ⓘ opens the detail popover;
  popovers follow the selection-popup dismissal contract (Escape /
  outside click / anchor off-screen via IntersectionObserver).
- tasksViewMode pref (graph default) with a select row in settings;
  58 new copy keys across zh/en/ja + 18 third-language dictionaries;
  dead CSS from the old tree/dock pruned.
- Tests: 6 new page-interaction specs (auto-collapse, both-mode toggle,
  jump, fold, popover); jobs-view suite re-pointed at the popover;
  prefs/builtins/smoke lock tests updated for the new pref.

src/client/builtins/tabs.tsx

@@ -137,12 +137,30 @@ export function builtinTabs(): readonly TabDescriptor[] {
           key: 'autoOpenJobs',
           title: () => t('settingsJobsTitle'),
           desc: () => t('settingsJobsDesc'),
+        }, {
+          key: 'tasksViewMode',
+          type: 'select',
+          title: () => t('settingsViewModeTitle'),
+          desc: () => t('settingsViewModeDesc'),
+          options: [
+            {
+              value: 'graph',
+              title: () => t('settingsViewModeGraph'),
+              desc: () => t('settingsViewModeGraphDesc'),
+            },
+            {
+              value: 'tree',
+              title: () => t('settingsViewModeTree'),
+              desc: () => t('settingsViewModeTreeDesc'),
+            },
+          ],
         }],
       },
-      component: ({ ctx, scope, visible, onSubagentJump }) => (
+      component: ({ ctx, store, scope, visible, onSubagentJump }) => (
         <SubagentView
           sessionId={scope.sessionId}
           ctx={ctx}
+          store={store}
           active={visible}
           onOpenChild={(address) => { onSubagentJump?.(address.childSessionId) }}
         />