viewer: Pan + ZoomExtents + 표준 뷰 단축키

camera.rs:
- pan(dx, dy): Shift+중간버튼으로 target 이동 (화면 평면 이동)
- zoom_extents(mn, mx): E키로 전체 씬 맞춤
- set_standard_view(StandardView): 축 고정 뷰
- StandardView: Top(7) / Front(1) / Right(3) / Left(4) / Iso(Home)

lib.rs:
- shift_pressed 추적 (ModifiersChanged)
- Shift+중간버튼 드래그 → pan
- E → ZoomExtents
- 1/3/4/7/Home → 표준 뷰 스냅
- scene_mn/mx 저장 → zoom_extents에 전달

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cimery/crates/viewer/src/camera.rs

@@ -22,6 +22,16 @@ impl CameraUniform {
 
 // ─── Camera ──────────────────────────────────────────────────────────────────
 
+/// Standard axis-aligned views (Revit numpad convention).
+#[derive(Debug, Clone, Copy)]
+pub enum StandardView {
+    Top,    // Numpad 7
+    Front,  // Numpad 1
+    Right,  // Numpad 3
+    Left,   // Numpad 4 / Ctrl+Numpad3
+    Iso,    // Home
+}
+
 /// Orbit camera — spherical coordinates around a fixed target point.
 ///
 /// All distances in millimetres (scene units).
@@ -94,6 +104,42 @@ impl Camera {
         self.radius = (self.radius * (1.0 - delta * 0.1)).max(100.0);
     }
 
+    /// Pan target by screen-space delta (Shift + middle mouse).
+    ///
+    /// Moves the orbit centre so the object stays under the cursor.
+    pub fn pan(&mut self, delta_x: f32, delta_y: f32) {
+        let eye      = self.eye();
+        let view_dir = (self.target - eye).normalize();
+        let right    = view_dir.cross(Vec3::Y).normalize();
+        let up       = right.cross(view_dir).normalize();
+        let scale    = self.radius * 0.001;   // pan speed proportional to zoom
+        self.target -= right * delta_x * scale;
+        self.target += up   * delta_y * scale;
+    }
+
+    /// Zoom-extents: fit the given bounding box into view.
+    pub fn zoom_extents(&mut self, mn: [f32; 3], mx: [f32; 3]) {
+        let c = Vec3::new(
+            (mn[0] + mx[0]) * 0.5,
+            (mn[1] + mx[1]) * 0.5,
+            (mn[2] + mx[2]) * 0.5,
+        );
+        let diag = Vec3::new(mx[0]-mn[0], mx[1]-mn[1], mx[2]-mn[2]).length();
+        self.target = c;
+        self.radius = (diag * 0.75).max(1000.0);
+    }
+
+    /// Snap to a standard axis-aligned view (Revit numpad convention).
+    pub fn set_standard_view(&mut self, view: StandardView) {
+        match view {
+            StandardView::Top   => { self.yaw = 0.0;  self.pitch =  std::f32::consts::FRAC_PI_2 - 0.01; }
+            StandardView::Front => { self.yaw = std::f32::consts::PI; self.pitch = 0.0; }
+            StandardView::Right => { self.yaw = std::f32::consts::FRAC_PI_2; self.pitch = 0.0; }
+            StandardView::Left  => { self.yaw = -std::f32::consts::FRAC_PI_2; self.pitch = 0.0; }
+            StandardView::Iso   => { self.yaw = std::f32::consts::FRAC_PI_4; self.pitch = 0.35; }
+        }
+    }
+
     /// Update aspect ratio on window resize.
     pub fn resize(&mut self, width: u32, height: u32) {
         self.aspect = width as f32 / height.max(1) as f32;