#23073 cmux-next Chief: Subagents menu rows run chief.openSubagent, not an inline selector

check-menu-actions.py (the "Menu rows run registered actions, not inline selectors" step of cmux-next guards) fails on feat-cmux-next because the Chief pane's Subagents menu built its rows with an inline #selector(openSubagent(_:)). This PR makes each row run a new registered action, chief.openSubagent, so that check passes. The rows behave the same as before.

• New action: chief.openSubagent ("Open Chief Subagent") goes in SidebarSectionActionCatalog. Its target is the subagent row's sidebar item (sidebar-item:<id>). It is exempt from the palette and CLI verb as focusMove, like home.openConversation. Its title is translated into the catalog's 21 languages.
• Binding: ChiefSidebar.bind binds it to the existing activate(LayoutItemID(target.id), registry:) path, the same path a click on the sidebar row takes.
• Menu rows: ChiefPaneTools.subagentsMenu() builds each row through registry.makeContextMenu, then sets the subagent's own title and status tooltip, with no icon and no key. The @objc openSubagent selector is gone.
• Behavior: a row is now enabled only while the action is bound and allowed by policy. In the app it is always bound, so nothing visible changes.
• Generated files: the action exports (plans/cmux-next/action-surfaces.json, actions.md) are regenerated by PR autofix on a Mac runner, not by hand.

Testing

• Red, on base 92d14b214ff: python3 scripts/cmux-next/check-menu-actions.py fails on ChiefPaneTools.swift, the same failure as the base red.
• Green, on head: the same command passes with "38 inline menu rows in 29 baselined files, none new".
• New test: HomeDockTabRowToolsTests.eachSubagentRowOpensItsSessionThroughTheRegisteredAction (commit 1). It checks through ActionRegistry.menuRun(of:) that each row runs chief.openSubagent on its own sidebar-item:<row id> with no arguments, and that each row keeps its title and tooltip.

Observed / Not run

• Observed: check-menu-actions.py passes, prepush-gate.py reports no new violations and check-no-godfiles.sh passes on the changed files. localization_catalog.py check fails exactly as it does on base, with no error in the files changed here.
• Not run: no Swift compile or tests locally (Mac compiles run on CI). The new test, ActionSurfaceParityTests and ActionContractTests run on CI.

Changelog

none

Agent session: huge-blue

🤖 Generated with Claude Code

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Summary by cubic

The Chief pane's Subagents menu rows now run the registered chief.openSubagent action through the action registry, instead of an inline selector, so the check-menu-actions.py guard passes. Rows behave identically to before.

• New chief.openSubagent action binds to the same activation path as a click on the sidebar row; its target is the row's sidebar-item:<id>, and it is exempt from the palette and CLI verb as focusMove.
• Menu rows are rebuilt from the registry, then retitled with the subagent's own title and status tooltip, with no icon or key.
• Added tests asserting each row runs the action on its own row's sidebar item with no arguments, and that the action is not a palette row.
• A row is enabled only while the action is bound and allowed by policy; in the app it is always bound, so nothing visible changes.