Preview a screen as a chosen caller and state #1390

Part of the epic #1387.

Scenario this serves. An application sells a plan per asset (a vessel in a fleet, a site, a workspace), not per customer. Which views, API operations and tools a caller may use depends on the plan of the specific asset they act on. Today a policy decides from the caller (role, claim) and from the arguments of the command or query. It cannot decide from state the application has recorded, such as the asset's plan.

Problem

A prototype of a screen shows every element. With caller-aware availability (Cratis/Screenplay#335) and state-reading policies, what is shown depends on who looks and on the state of what they look at.

Proposal

In the preview and on the board, let the person choose a caller and some state (for example an asset on a given plan) and see the screen as that caller would: gated actions hidden or unavailable, with the reason on hover. The server still decides; the preview is a design aid, not a test of enforcement.

Depends on

Cratis/Screenplay#335 and the generated-application work in Cratis/Stage (same epic).

Done when

Switching the chosen plan in the preview shows and hides the plan-gated elements, and the reason shown matches the policy that gates them.

Epic: #1387.
Siblings: Cratis/Screenplay#1230, Cratis/Screenplay#1231, Cratis/Screenplay#1232, Cratis/Screenplay#1233, Cratis/Screenplay#1234, Cratis/Arc#3764, Cratis/Arc#3765, Cratis/Arc#3766, Cratis/Chronicle#5765, Cratis/Stage#1048, Cratis/Stage#1049, Cratis/Stage#1050, #1388, #1389, #1390.