exp: 轮次46-47——select=pre(打分地平线=被执行前缀终点)正向，两 seed 复现

2 s 误差比逐题符号检验 s0 192好/64差 p=4.9e-16、s1 191/65 p=1.5e-15；时限内(≤1.3×老师)
0.2656→0.3320(+6.64pp)、0.2969→0.3398(+4.30pp)；行程比 −0.171/−0.171；碰撞仍 0、超 VMAX 仍 0。
到达只 +5/+3 题(McNemar p=0.42/0.68 ⇒ 噪声)，故不改默认口径、作可选口径入库。
代价：到达题末态误差 0.22→0.42 mm(判据壳 1 mm 内，余量 4.6×→2.4×)，两 seed 都涨。

对照可比性先证：控制臂 tie0 与轮次42 round42_K8cb1 的 22/22 键逐位相同 ⇒ 该配方跨窗口确定性
复现，本轮起新杠杆可用单臂对已落盘控制。

实现：select='pre' 用 fut[:,:,commit_n-1] 的终点误差(同一次 goal_err 只换点集)；两条可手算正对照
(前缀好/末端差 vs 末端好/前缀差 ⇒ 两口径必须选相反候选) + 不变式(commit_n=16 时与 endpoint 同选)；
49 项测试绿；n=16 冒烟证非惰性。候选表同步修准：backoff/ep_waste 两行状态改判掉，#29/#30 登记。

docs/experiment_round46_pre16_smoke.json

@@ -0,0 +1,96 @@
+{
+  "config": {
+    "ckpt": "ml/runs/base_dag2_dag1/best.pt",
+    "samples": "ml/data/samples",
+    "tasks": null,
+    "split": "val",
+    "n": 16,
+    "K": 8,
+    "commit": 2,
+    "fb": 2.2,
+    "ki": 0.0,
+    "fb_scale": 0.0,
+    "fb_near": 0.2,
+    "fb_fallback": 0.0,
+    "kdecay": 0.9,
+    "kimax": 0.5,
+    "fb_every": 1,
+    "safety_try": 0,
+    "sel_w": 0.1,
+    "dls_safety": 1,
+    "fb_clear": 0.0,
+    "fb_cmin": 0.3,
+    "sub_refresh": 0,
+    "fb_block_gain": 0.5,
+    "dump": null,
+    "out": "docs/experiment_round46_pre16_smoke.json",
+    "trace": null,
+    "select": "pre",
+    "replan": "empty",
+    "safety": 1,
+    "partial": 1,
+    "inc_cap": 1,
+    "gap_margin": 0.0,
+    "cert_batch": 1,
+    "steps": 1,
+    "z_scale": 1.0,
+    "len_w": 0.0,
+    "tie": 0,
+    "backoff": 0,
+    "max_sec": null,
+    "seed": 0,
+    "dls": "analytic",
+    "device": "cuda"
+  },
+  "batch_size": 256,
+  "batch_seed_rule": "same seed per batch",
+  "checkpoint_sha256": "f7f686fd8ee92fb6948fbcc4ee954636065ad87bb54f661c4f8f575bc16c2ce1",
+  "tasks_sha256": "7b7c219c70d15b280682fe0626192b267f0e4dfd843b1e70fb279e148eb6eaa3",
+  "kin_fp": "2ebcbf17",
+  "act_scale": 1.0,
+  "metrics": {
+    "n": 16,
+    "n_ref": 16,
+    "success": 0.375,
+    "collision_free_success": 0.375,
+    "time_ok_1p3": 0.25,
+    "collision_rate": 0.0,
+    "collision_steps_mean": 0.0,
+    "travel_ratio_median": 2.6735622882843018,
+    "time_mean_s": 2.763333320617676,
+    "brakes_mean": 21.9375,
+    "start_fail": 0.0,
+    "goal_ratio_2s": 0.4253818392753601,
+    "err_fail_med": 223.724365234375,
+    "err_success_med": 0.7986489534378052,
+    "dls_share": 0.5625,
+    "time_budget": "teacher×2(≥3 s)",
+    "speed_ratio_p50": 1.0000016689300537,
+    "speed_ratio_p95": 1.0000053644180298,
+    "speed_ratio_max": 1.0000101327896118,
+    "over_vmax_rate": 0.0,
+    "accel_ratio_p95": 1.0000016689300537,
+    "accel_ratio_max": 1.0000016689300537,
+    "reverse_p50": 0.23239436745643616,
+    "reverse_mean": 0.22883012890815735,
+    "reverse_moving_p50": 0.29054054617881775,
+    "moving_share_p50": 0.9583333134651184,
+    "brake_rate_mean": 0.12535713613033295,
+    "brake_rate_p50": 0.0057142856530845165,
+    "brake_rate_p90": 0.3257142901420593,
+    "stuck_share": 0.3125,
+    "n_plans_mean": 175.0,
+    "success_reachable": 0.375,
+    "by_cat": {
+      "A": [
+        8,
+        4
+      ],
+      "B": [
+        8,
+        2
+      ]
+    }
+  },
+  "simulation_wall_s": 31.1417752999987
+}