feat(viewer): widen first-person walkthrough FOV to 60°

The walkthrough rode the default 50° orbit camera, which feels cramped on
foot. Both walkthrough controllers (baked GlbWalkthroughController and the
parametric WalkthroughControls fallback) now set a shared WALKTHROUGH_FOV = 60
on enter and restore the prior FOV on exit, leaving orbit framing untouched.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/viewer/src/components/viewer/glb-walkthrough-controller.tsx

@@ -15,6 +15,7 @@ import {
   Mesh,
   MeshBasicMaterial,
   type Object3D,
+  type PerspectiveCamera,
   Quaternion,
   Vector3,
 } from 'three'
@@ -24,6 +25,7 @@ import { useGLTFKTX2 } from '../../hooks/use-gltf-ktx2'
 import { SCENE_LAYER } from '../../lib/layers'
 import useViewer from '../../store/use-viewer'
 import BVHEcctrl, { type BVHEcctrlApi, type MovementInput } from './bvh-ecctrl'
+import { WALKTHROUGH_FOV } from './walkthrough-controls'
 
 // Eye/capsule geometry mirrors the editor's first-person controller so the
 // baked walkthrough feels identical. The capsule centre sits below the eye; the
@@ -264,6 +266,22 @@ export function GlbWalkthroughController({ url }: { url: string }) {
     }
   }, [])
 
+  // Widen FOV while walking; the baked walkthrough rides the default 50° orbit
+  // camera, which feels cramped on foot. Keyed on `camera` so it re-applies if
+  // the instance swaps (e.g. the ortho→perspective switch above), restoring the
+  // prior FOV on exit.
+  useEffect(() => {
+    const cam = camera as PerspectiveCamera
+    if (!cam.isPerspectiveCamera) return
+    const prevFov = cam.fov
+    cam.fov = WALKTHROUGH_FOV
+    cam.updateProjectionMatrix()
+    return () => {
+      cam.fov = prevFov
+      cam.updateProjectionMatrix()
+    }
+  }, [camera])
+
   useEffect(() => {
     worldRef.current = world
     if (world) {

packages/viewer/src/components/viewer/walkthrough-controls.tsx

@@ -3,12 +3,18 @@
 import { PointerLockControls } from '@react-three/drei'
 import { useFrame, useThree } from '@react-three/fiber'
 import { useCallback, useEffect, useRef } from 'react'
-import { Vector3 } from 'three'
+import { type PerspectiveCamera, Vector3 } from 'three'
 import useViewer from '../../store/use-viewer'
 
 const MOVE_SPEED = 5
 const EYE_HEIGHT = 1.6
 
+// First-person FOV. The orbit camera is 50° (set on the Canvas), which feels
+// cramped on foot; ~60° vertical (~90° horizontal at 16:9) restores peripheral
+// awareness without wide-angle distortion. Applied only while walking — both
+// walkthrough controllers read this and restore the orbit FOV on exit.
+export const WALKTHROUGH_FOV = 60
+
 const _direction = new Vector3()
 const _forward = new Vector3()
 const _right = new Vector3()
@@ -26,6 +32,20 @@ export const WalkthroughControls = () => {
     }
   }, [walkthroughMode, camera])
 
+  // Widen FOV while walking; restore the orbit FOV on exit.
+  useEffect(() => {
+    if (!walkthroughMode) return
+    const cam = camera as PerspectiveCamera
+    if (!cam.isPerspectiveCamera) return
+    const prevFov = cam.fov
+    cam.fov = WALKTHROUGH_FOV
+    cam.updateProjectionMatrix()
+    return () => {
+      cam.fov = prevFov
+      cam.updateProjectionMatrix()
+    }
+  }, [walkthroughMode, camera])
+
   // Keyboard handlers
   useEffect(() => {
     if (!walkthroughMode) return