gr2: binary-search the curve knot (upper_bound) when knots are ascending

Curve::eval scanned every knot to find the first one past t; long animation
tracks made that the top of CPythonCharacterManager::Deform. Knots are checked
for ascending order at load and unsorted curves keep the linear scan, so the
chosen knot is unchanged. Desktop live game: Deform samples 93 -> 58.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/gr2/include/gr2/types.h

@@ -103,6 +103,7 @@ struct Curve {
     uint32_t           dim    = 0;         // 3=vec, 4=quat, 9=3x3 scaleshear
     std::vector<float> knots;              // KnotCount 个
     std::vector<float> controls;           // KnotCount * dim 个
+    bool               knots_sorted = true; // 升序 → eval 二分找 knot；否则按原样线性扫
     bool               empty() const { return knots.empty() || dim == 0; }
     // t 处求值，写 dim 个 float 到 out（identity 由调用方给）。
     void eval(float t, float* out) const;

src/gr2/src/gr2_anim.cpp

@@ -76,6 +76,7 @@ void File::Impl::read_old_curve(Ref curve_obj, Ref curve_type, Curve& out) {
     };
     read_farr(*mK, out.knots);
     read_farr(*mC, out.controls);
+    out.knots_sorted = std::is_sorted(out.knots.begin(), out.knots.end());
     out.dim = out.knots.empty() ? 0 : uint32_t(out.controls.size() / out.knots.size());
     if (out.dim && out.knots.size() * out.dim != out.controls.size()) out.dim = 0;  // 不一致 → 弃
 
@@ -218,8 +219,14 @@ void Curve::eval(float t, float* out) const {
     }
     if (t <= knots[0])      t = knots[0];
     if (t >= knots[n - 1])  t = knots[n - 1];
+    // 第一个 > t 的 knot（找不到 → n-1）；升序时二分
     int i = (int)n - 1;
-    for (uint32_t k = 0; k < n; ++k) if (knots[k] > t) { i = (int)k; break; }
+    if (knots_sorted) {
+        const int k = int(std::upper_bound(knots.begin(), knots.end(), t) - knots.begin());
+        if (k < (int)n) i = k;
+    } else {
+        for (uint32_t k = 0; k < n; ++k) if (knots[k] > t) { i = (int)k; break; }
+    }
     if (i < 1) i = 1;
 
     const int span = (degree == 1) ? 2 : 3;   // 本 span 的控制点数 = degree+1