Tear-out without a cross-window sort group leaves no way back, silently

Context

2026-10-07: in the installed Fleet Manager, the operator and @neo-gpt-sophie tore a tab out of the app, dropped it outside, then dragged the new window back over the app. The main app showed no drop zones. Workstation, which publishes a cross-window sort group, docked a committed popup moved over main back into it in @neo-fable's 2026-09-26 probes. The difference is configuration that nothing checks.

The Problem

A workspace can turn tear-out on and still have no way back, and nothing says so:

• enableDockTearOutLifecycle: true makes Workspace#getDockProjectionOptions return {enableDockTearOut: true, ...tearOutHandlers} (src/dashboard/dock/Workspace.mjs). Tear-out works.
• The way back needs a cross-window sort group. LayoutAdapter threads crossWindowSortGroup into each tab zone's sortGroup, the key DragCoordinator registers zones under. The workspace composes its default cross-window Participation only when it publishes one (Workspace.mjs:61, window/Participation.mjs:636). Without it, a window dragged back finds no registered target, and no drop zones are painted.
• LayoutAdapter defaults the group to null. The base hook publishes none.

Fleet Manager's cockpit (apps/agentos/view/fleet/cockpit/Container.mjs, VesselContainer.mjs in neomjs/neo-agent-institution) enables the lifecycle but publishes no group. Workstation publishes one explicitly (apps/workstation/view/VesselWorkspace.mjs, PopupWorkspace.mjs). WebStudio hit the same omission on 2026-09-03; its fix added the group. #18197 closed the sibling case, a lost enableDockTearOut, with a throw at projection. The sort group has no such guard.

The Fix

Make "tear-out on, no way back" impossible to ship silently. Two shapes:

1. Guard (smallest; safe for 13.2): at projection, when enableDockTearOut is on and no crossWindowSortGroup is published, report it once (console.warn naming the workspace class), so the omission shows in the first manual test. #18197's throw is the precedent for escalating later. A throw now would break every consumer that upgrades before publishing a group.
2. Default: when the lifecycle is on and no group is published, use a default group. Whether unrelated workspaces may then share a group is a design decision for the docking design record's §2.3 owner, not this ticket.

Recommendation: ship 1 with 13.2, and decide 2 after the cut.

Acceptance Criteria

• A workspace projected with the tear-out lifecycle on and no crossWindowSortGroup reports the omission once, naming the workspace class (unit).
• A workspace that publishes a group, such as Workstation's VesselWorkspace, reports nothing (unit).
• Workstation's tear-out and return gestures are unchanged (existing e2e).

Out of Scope

• Fleet Manager's own fix, publishing its group (Institution; routed to its owner).
• A default group (shape 2): decided after the cut.

Related

#18197 (the sibling guard for enableDockTearOut) · #19350 (the default cross-window participation for a published group) · neomjs/neo-agent-institution#12 (where the operator met it)

Live latest-open sweep: org search "crossWindowSortGroup" and "tear-out no way back drop zones" (open): only neomjs/neo-agent-institution#12, which mentions it; no equivalent. A2A: no claim on the dock sort group.

Origin Session ID: 9aa8aa9b-2502-458b-976b-eec8a223218e

Retrieval Hint: "dock tear-out crossWindowSortGroup no drop zones drag back Participation silent"