[T-Crypt]

Step 3 of the switchboard plan: the read side the phone board will draw.

Change

GET /v1/berth/board (keyed) answers one node:

{name, reachable, cards: [{index, name, state, total, used, holders}],
 engines: [{name, gui, api, launch, state, message, detail, code, card, stoppable, models: [{id, loaded}]}]}

• Card state: free, held, draining, passthrough (in a VM) or probe-failed.
• Engine rows are the /gui/ board's rows, plus stoppable (holds the card under an active lease that isn't pinned) and its models: the engine's own list while it is up, its serves otherwise. A model's loaded comes from berthd's engine reader, which for llama-swap reads /running.
• Built in the gateway because only the gateway knows about a start that is still in flight. The harbor will read this endpoint with the node key and, in the fleet, merge one board per node.
• guiStateAll becomes guiRows(ctx, node), so the board and /gui/state share one berthd status read.

Proof

• TestBoard: idle node (card free), then a switch. The card becomes held by strata/active, strata is up and stoppable with its model, and a stopped comfyui is launchable but not stoppable, with its serves.
• TestBoardOf (table): berthd unreachable, held with one llama-swap model ready and one starting, a pinned game (not stoppable), draining, and in a VM.
• build, gofmt, vet, go test ./..., Windows build and vet, golangci-lint (0 issues), -race -count=3.

Not run against the live gateway, for the same reason as #141.