feat(target): tar.availableVessels + tar.switchVessel — list and fly to vessels

[jonpepler]

Summary

Two new keys in the tar.* family that finally make tar.setTargetVessel usable and add a flight-scene "fly to vessel":

Key	Kind	Returns
tar.availableVessels	read	[{ index, name, type, situation, body, position }, …] — every vessel except the active vessel and the Flag / EVA / Debris / Unknown types
tar.switchVessel[index]	action	Flies the player to the given vessel — the same operation as the Tracking Station "Fly" button, callable from a flight scene

tar.setTargetVessel[index] already worked, but it had no companion key to enumerate the indices it expects, so in practice it was unusable without an external source of indices. tar.availableVessels closes that loop — both keys share the same index space, and the new position field gives a client enough to sort the list by distance.

Wire shape

{
  "tar.availableVessels": [
    {
      "index": 13,
      "name": "Munar Orbiter",
      "type": "Probe",
      "situation": "ORBITING",
      "body": "Mun",
      "position": [184523.4, 12055.2, -3217.8]
    }
  ]
}

• index — the exact FlightGlobals.Vessels[index] slot. Non-contiguous once filtered vessels punch holes in the array.
• type — Vessel.vesselType: Ship, Probe, Lander, Plane, Rover, Station, Base, Relay, SpaceObject, …
• situation — Vessel.Situations: LANDED / SPLASHED / PRELAUNCH / FLYING / SUB_ORBITAL / ORBITING / ESCAPING / DOCKED.
• body — name of the orbited body. Sun-orbiting vessels report "Sun".
• position — vector in the active vessel's local frame (transform.InverseTransformPoint); its magnitude tracks the in-game distance readout. Omitted when there is no active vessel, so the key is flight-scene only.

Design notes

• Walks FlightGlobals.Vessels without re-sorting, so the indices match KSP's internal addressing one-for-one and stay aligned with tar.setTargetVessel. A client that wants distance order sorts on position itself.
• Filter is deliberately minimal. Flag / EVA / Debris / Unknown covers everything a client shouldn't normally target. SpaceObject (asteroids and comets) is kept — it's a legitimate target.
• tar.switchVessel saves state before switching. HighLogic.CurrentGame.Updated() + GamePersistence.SaveGame preserves the current vessel's mid-flight pose, fuel, and heat so they're restored on switch-back. This mirrors what the Tracking Station's "Fly" button does internally. The args/range/HighLogic.CurrentGame guards return early before any scene change is attempted.

Validation

dotnet build clean. OpenAPI and docs/api-schema.json regenerated to include both keys. Exercised live against a running KSP install on 2026-05-15: the array carries every documented field with the active vessel correctly absent and indices non-contiguous; tar.setTargetVessel and tar.switchVessel both act on the right vessel by index; position magnitude tracks tar.distance; switching away and back restores the saved pose and fuel; and an out-of-range index returns false with no scene change. The Flag / EVA / Debris / Unknown filter holds while SpaceObject rows pass through.

Behavioural notes

• Like the other annotated IsAction keys, the HTTP response body returns false even on success. The action is queued onto the Unity main thread and the state change echoes back over the WebSocket stream, not the HTTP response.
• tar.availableVessels indices can shift when the active vessel changes (KSP reshuffles FlightGlobals.Vessels on focus change), so clients should treat them as per-snapshot selectors, not stable identifiers.