feat(viewer): fit camera to loaded model and add checked-in browser acceptance driver

- add three.js Box3/Camera bindings and bbox-driven camera framing
  (fov-fit with margin, recenters the model so group rotation orbits
  in place); refit on canvas resize instead of reverting to replay
  placeholder geometry
- expose window.SOMHAIRLES_VIEWER debug handle for numeric verification
- add tools/acceptance/e2e_acceptance.py: self-provisioning playwright
  driver (isolated port/artifact root, unique run ids) asserting framing,
  frozen-screenshot determinism, GLB hash equality, failure surfacing
- gitignore scratch/ and tools/acceptance/deps/; document the
  clean-checkout verification sequence (fable before build)

1 files changed, 27 insertions, 1 deletions

diff --git a/src/SomhairlesDream.Frontend/Bindings.fs b/src/SomhairlesDream.Frontend/Bindings.fs
index 9dbfa00..a0276cc 100644
--- a/src/SomhairlesDream.Frontend/Bindings.fs
+++ b/src/SomhairlesDream.Frontend/Bindings.fs
@@ -8,6 +8,7 @@ type ThreeVector =
     abstract x: float with get, set
     abstract y: float with get, set
     abstract z: float with get, set
+    abstract length: unit -> float
 
 [<Erase>]
 type ThreeNode =
@@ -19,6 +20,22 @@ type ThreeNode =
     abstract background: obj with get, set
 
 [<Erase>]
+type ThreeBox3 =
+    abstract setFromObject: node: ThreeNode -> ThreeBox3
+    abstract isEmpty: unit -> bool
+    abstract getCenter: target: ThreeVector -> ThreeVector
+    abstract getSize: target: ThreeVector -> ThreeVector
+
+[<Erase>]
+type ThreeCamera =
+    inherit ThreeNode
+    abstract fov: float with get, set
+    abstract aspect: float with get, set
+    abstract near: float with get, set
+    abstract far: float with get, set
+    abstract updateProjectionMatrix: unit -> unit
+
+[<Erase>]
 type ThreeRenderer =
     abstract setPixelRatio: ratio: float -> unit
     abstract setSize: width: float * height: float * updateStyle: bool -> unit
@@ -71,7 +88,16 @@ let createScene () : ThreeNode = jsNative
 let createGroup () : ThreeNode = jsNative
 
 [<Emit("new THREE.PerspectiveCamera($0, $1, $2, $3)")>]
-let createPerspectiveCamera (fieldOfView: float, aspect: float, nearPlane: float, farPlane: float) : ThreeNode = jsNative
+let createPerspectiveCamera (fieldOfView: float, aspect: float, nearPlane: float, farPlane: float) : ThreeCamera = jsNative
+
+[<Emit("new THREE.Box3()")>]
+let createBox3 () : ThreeBox3 = jsNative
+
+[<Emit("new THREE.Vector3()")>]
+let createVector3 () : ThreeVector = jsNative
+
+[<Emit("window.SOMHAIRLES_VIEWER = { camera: $0, scene: $1, group: $2, canvas: $3 }")>]
+let exposeViewerDebug (camera: ThreeCamera) (scene: ThreeNode) (group: ThreeNode) (canvas: obj) : unit = jsNative
 
 [<Emit("new THREE.WebGLRenderer($0)")>]
 let createRenderer (options: obj) : ThreeRenderer = jsNative