#22852 cmux NEXT: the Chief's status, subagents and actions in its pane's tab row

Follows #22759 (merged): the sidebar's Chief item.

Summary

Leo asked (2026-10-20) for the Chief's pane to get a top-right area like a normal workspace's, holding its status, subagents and actions, in the same place as a chat's tools in the pane's tab row (PaneTabRowSharing, #22655, #22758, #22769).

• The docked Home's Messages view (the Chief's chat) shares its pane's tab row. HomeDockSwitchView conforms to PaneTabRowSharing:
  • tabRowToolsWidth / tabRowToolsNeed give the shown view's tools' width (tabRowToolsNeed is kept after the row ends).
  • The tools sit at the row's trailing end, left of the pane's own toolbar.
  • The view lays its content under the row, and sets setTabRowCover, only while the tools are in the row.
  • Channels has no tools; switching to it tells the pane.
• The page-tab wrapper forwards the row. InternalPageView forwards the row to its page through a new PaneTabRowForwarding protocol in CmuxNextDesign. That is a one-line conformance, so CmuxNextApp does not grow.
• ChiefPaneTools (CmuxNextAgentLanes) draws the tools:
  • the Chief's status mark: the same ChiefSidebar.status as the sidebar item; its slot is kept while idle;
  • Subagents: every subagent with its status; a row opens like its sidebar row;
  • Chief Actions: Stop Chief, Chief Settings, the Memory Inspector, Usage, New Chief, all from the catalog with their shortcuts.
• Wiring. ChiefSidebar.bind registers the tools factory (HomeDockSwitchView.makeRowTools).
• Off switch. The tools follow ChromeTunables.tabRowTools: with it off, there are no tools.

Testing

• HomeDockTabRowToolsTests (new):
  • the width is reported;
  • fitsTabRow holds and fails in the right rooms;
  • the tool and content frames are right with the row offered and without it;
  • Channels reports no tools, keeps the need and tells the pane once.
• prepush-gate.py: no new violations. check-app-size.sh --base origin/feat-cmux-next: OK.

Observed / Not run

• Observed: the static gate and the size cap, run locally.
• Not run: the Swift build and the tests. Per the repo rules, they run on CI, not on this Mac. I have not dogfooded this in a tagged build.

Changelog

• Added: The Chief's pane shows the Chief's status, its subagents and its actions at the right end of its tab row.

Strings: 2 new keys (chief.tools.subagents, chief.tools.actions) in 21 locales, in a new CmuxNextAgentLanes string catalog.

Agent session: cosmic-gray

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