Dock example: perspective toolbar consumes ~51% viewport height (missing flex reset)

Context

The standalone dock example (examples/dashboard/dock) is the docking cornerstone's live regression surface and the base the demo work builds on. It currently renders with a broken vertical layout — surfaced by the operator during a live review of the #14771 tab-overflow verification.

The Problem

The Perspectives toolbar renders at 368.5px tall on a 720px viewport (~51%) with a large empty gap above and below its buttons, pushing the dock zones down into the bottom half of the screen. Verified live (getBoundingClientRect().height === 368.5).

Root Cause

createPerspectiveToolbar() (MainContainer.mjs:261) returns the toolbar config with no flex, while buildWorkspaceItems() sets dockConfig.flex = 1. In the root vbox, the unset toolbar inherits a growing default and splits the height ~50/50 with the dock. The toolbar's own hbox align:'center' then vertically centers the buttons inside that over-tall element — the empty band above and below.

The Fix

Set flex: 'none' on the perspective toolbar config → it sizes to content, the dock's flex: 1 takes the remaining viewport. Verified live: injecting the flex reset drops the toolbar 368.5px → 42px and the dock fills the rest.

Acceptance Criteria

• The perspective toolbar renders at content height (~42px), not a viewport fraction.
• The dock zones fill the remaining viewport height.
• No regression to the toolbar's controls (Operator/Review/Save/Delete) or their handlers.

Out of Scope

The broader "default → stunning" visual polish (unstyled panels, spacing, theming) is already captured — #14780 (motion/choreography "stunning" standards), #14681 (light/dark theme tokens for demos), #14589 (the polished dock choreography showcase). This ticket is the concrete layout defect only.

Related

Parent #13158 (QT-parity docking) · the example is the #13247 slice surface (Vega). Found during #14771 live verification.