取景视角限定在 (0, 180)，非法值回落到默认视角

- packages/model3d-viewer/src/framing.ts：新增 normalizeFovDegrees，fovDegrees 只在 (0, 180) 内采用，>=180 时 tan(halfFovY) 非正会把 limitY/limitX 与 fallbackDistance 算成 0 或负数，污染取景距离与 near/far
- packages/model3d-viewer/src/framing.test.ts：补 180 / 360 / 0 / 负数 / NaN 回落到默认视角的用例

packages/model3d-viewer/src/framing.test.ts

@@ -146,6 +146,25 @@ describe('computeModel3dViewerFitDistance', () => {
 });
 
 describe('createModel3dViewerFitSolver', () => {
+  it('视角超出 (0, 180) 时回落到默认视角，不把取景距离算成非正数', () => {
+    for (const fovDegrees of [180, 360, 0, -45, Number.NaN]) {
+      const solver = createModel3dViewerFitSolver({
+        center: { x: 0, y: 0, z: 0 },
+        aspect: 1,
+        fovDegrees,
+      });
+
+      expect(solver.resolve(), String(fovDegrees)).toBeCloseTo(
+        createModel3dViewerFitSolver({
+          center: { x: 0, y: 0, z: 0 },
+          aspect: 1,
+          fovDegrees: MODEL3D_VIEWER_CAMERA_FOV_DEGREES,
+        }).resolve(),
+        6,
+      );
+    }
+  });
+
   it('喂包围盒角点时与包围盒口径一致', () => {
     const expected = computeModel3dViewerFitDistance({ box: CUBE, aspect: 2 });
 

packages/model3d-viewer/src/framing.ts

@@ -71,6 +71,19 @@ function normalizePositive(value: number, fallback: number): number {
   return Number.isFinite(value) && value > 0 ? value : fallback;
 }
 
+/**
+ * 取景视角必须落在 (0, 180)：>=180 时 `tan(halfFovY)` 非正，`limitY/limitX` 与
+ * `fallbackDistance` 会算出 0 或负数，取景距离跟着变成负数并污染 near/far 与轨道范围。
+ */
+function normalizeFovDegrees(value: number | null | undefined): number {
+  return typeof value === 'number' &&
+    Number.isFinite(value) &&
+    value > 0 &&
+    value < 180
+    ? value
+    : MODEL3D_VIEWER_CAMERA_FOV_DEGREES;
+}
+
 function subtract(
   left: Model3dViewerVector3,
   right: Model3dViewerVector3,
@@ -152,10 +165,7 @@ export function createModel3dViewerFitSolver(
   input: Model3dViewerFitSolverInput,
 ): Model3dViewerFitSolver {
   const aspect = normalizePositive(input.aspect, FALLBACK_ASPECT);
-  const fovDegrees = normalizePositive(
-    input.fovDegrees ?? MODEL3D_VIEWER_CAMERA_FOV_DEGREES,
-    MODEL3D_VIEWER_CAMERA_FOV_DEGREES,
-  );
+  const fovDegrees = normalizeFovDegrees(input.fovDegrees);
   const fitFraction = normalizePositive(
     input.fitFraction ?? MODEL3D_VIEWER_FIT_FRACTION,
     MODEL3D_VIEWER_FIT_FRACTION,