feat: migrate simulation to physically-based unit system

Replace arbitrary game units with real-world measurements throughout
the simulation and viewer: planet orbits in AU, sizes in km, galaxy
positions in light-years. Add SimulationUnits helpers for conversions,
separate WarpSpeed from FtlSpeed for ships, fix FTL transit progress
to use galaxy-space distances, overhaul Lagrange point placement with
Hill sphere approximation, and update the viewer to scale and format
all distances correctly. Ships in FTL transit now render in galaxy view.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/viewer/src/viewerInteractionController.ts

@@ -2,6 +2,7 @@ import * as THREE from "three";
 import {
   completeMarqueeSelection,
   hideMarqueeBox,
+  pickSelectableHitAtClientPosition,
   pickSelectableAtClientPosition,
   updateHoverLabel,
   updateMarqueeBox,
@@ -17,6 +18,7 @@ import type {
   DragMode,
   Selectable,
   WorldState,
+  ZoomLevel,
 } from "./viewerTypes";
 
 export interface ViewerInteractionContext {
@@ -30,6 +32,7 @@ export interface ViewerInteractionContext {
   keyState: Set<string>;
   getWorld: () => WorldState | undefined;
   getActiveSystemId: () => string | undefined;
+  getZoomLevel: () => ZoomLevel;
   getSelectedItems: () => Selectable[];
   setSelectedItems: (items: Selectable[]) => void;
   getDragMode: () => DragMode | undefined;
@@ -247,10 +250,12 @@ export class ViewerInteractionController {
     updateHoverLabel({
       dragMode: this.context.getDragMode(),
       hoverLabelEl: this.context.hoverLabelEl,
-      selection: this.pickSelectableAtClientPosition(event.clientX, event.clientY),
+      hoverPick: this.pickSelectableHitAtClientPosition(event.clientX, event.clientY),
       activeSystemId: this.context.getActiveSystemId(),
+      zoomLevel: this.context.getZoomLevel(),
       world: this.context.getWorld(),
       point: this.context.screenPointFromClient(event.clientX, event.clientY),
+      camera: this.context.camera,
     });
   }
 
@@ -285,6 +290,18 @@ export class ViewerInteractionController {
     );
   }
 
+  private pickSelectableHitAtClientPosition(clientX: number, clientY: number) {
+    return pickSelectableHitAtClientPosition(
+      this.context.renderer,
+      this.context.raycaster,
+      this.context.mouse,
+      this.context.camera,
+      this.context.selectableTargets,
+      clientX,
+      clientY,
+    );
+  }
+
   private completeMarqueeSelection() {
     const selection = completeMarqueeSelection({
       renderer: this.context.renderer,