ui/phase-18: ship-class calc bridge with live designer preview

Wires pkg/calc/ship.go into the WASM Core boundary as seven thin
wrappers (DriveEffective, EmptyMass, WeaponsBlockMass, FullMass,
Speed, CargoCapacity, CarryingMass). The ship-class designer reads
Core through a new CORE_CONTEXT_KEY populated by the in-game layout
and renders a five-row preview pane (mass, full-load mass, max
speed, range at full load, cargo capacity) that updates reactively
on every form edit and on the player's localPlayer{Drive,Weapons,
Shields,Cargo} tech levels — three of which are now decoded from
the report's Player block alongside the existing localPlayerDrive.

CarryingMass is the seventh wrapper added to the original six-function
list so that "full-load mass" composes through pkg/calc/ functions
without putting math in TypeScript.

ui/frontend/src/lib/i18n/locales/en.ts

@@ -238,6 +238,13 @@ const en = {
 	"game.designer.ship_class.invalid.cargo_value": "cargo must be 0 or ≥ 1",
 	"game.designer.ship_class.invalid.armament_weapons_pair": "armament and weapons must be both zero or both nonzero",
 	"game.designer.ship_class.invalid.all_zero": "at least one value must be nonzero",
+	"game.designer.ship_class.preview.title": "preview at your tech levels",
+	"game.designer.ship_class.preview.mass": "mass",
+	"game.designer.ship_class.preview.full_load_mass": "full-load mass",
+	"game.designer.ship_class.preview.max_speed": "max speed (ly/turn)",
+	"game.designer.ship_class.preview.range": "range at full load (ly/turn)",
+	"game.designer.ship_class.preview.cargo_capacity": "cargo capacity per ship",
+	"game.designer.ship_class.preview.unavailable": "—",
 } as const;
 
 export default en;