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/prefs-shared.ts

@@ -22,6 +22,11 @@ export interface SidebarPrefs {
    * conversation (any new job id, not just the first one).
    */
   autoOpenJobs: boolean
+  /**
+   * The Tasks page's default presentation: the workflow graph canvas or the
+   * classic indentation tree (the in-page toggle still flips it ad hoc).
+   */
+  tasksViewMode: 'graph' | 'tree'
   /**
    * Whether the model-facing `sidebar_open` tool is injected into the
    * model's toolset — one tool that lets the model actively open a local
@@ -151,6 +156,7 @@ export type TitleBarScheme = typeof TITLE_BAR_SCHEMES[number]
 export const SIDEBAR_PREFS_DEFAULTS: SidebarPrefs = {
   autoOpenSubagent: true,
   autoOpenJobs: true,
+  tasksViewMode: 'graph',
   agentOpenTools: false,
   editorExplorer: false,
   workspaceFence: true,