修正朝上判断、接触高度与过期姿态目标

朝上判断误用平台轴、接触高度报旋转前数值、多点对准复用缓存姿态，且多点会话被复核入口拒绝；
现按修正计划改正并接通 autocal-multipoint-1.0 只读复核，缺失帧源如实报告而不补零。

离线验证：新回归在 dc5a6f8 上失败、此处通过，panel_check 通过，两截图点接触高度复现
19.0510 / 21.5781 mm；实机项未做，详见 .scratch/autocal-motion-fix/verification.md。

apps/autocal/docs/finger-debug-findings.md

@@ -53,7 +53,7 @@ With the corrected envelope, solved by closed form
 
 | Envelope | Worst residual | Within 0.5 deg | In range |
 |---|---|---|---|
-| pitch 360 deg, **yaw +-180 deg** (the machine) | **1.2e-06 deg** | 100% | **1032 / 1032** |
+| pitch 90 deg, **yaw +-180 deg** (the machine) | **1.2e-06 deg** | 100% | **1032 / 1032** |
 
 Every vertex is reachable, and the residual is at the floating-point floor rather
 than at any clamp. The "0.21 deg worst, genuinely clamped vertex" claim above was
@@ -65,11 +65,17 @@ the reachability evidence. Whether they help *repeatability* — a shorter pitch
 move, a better-conditioned contact — is a separate bench question, not a
 kinematic one.
 
-One thing the corrected solve did surface: **51 of 1032 vertices end inverted**,
-whichever closed-form branch is chosen, because the tool direction is
-antiparallel to the sensor's own up axis. That is the tool-polarity question, it
-needs the bench, and it is *not* visible in the residual. See
-`inverse-kinematics.md` → *Still open*.
+**Correction (motion-correction-plan.zh.md task 1).** This note used to claim that
+**51 of 1032 vertices end inverted** whichever branch is chosen, because the tool
+direction was antiparallel to the sensor's own up axis. That count came from
+`uprightness` comparing a platform axis through `to_sensor(np.eye(3)[1])`, which is
+the sensor's own **-Z** — a horizontal axis — so a body rolled about the vertical
+was reported as turned over. Measured against the post-mount nominal up (the tool
+axis) no exported vertex is inverted, and the corrected flag changes no vertex's
+branch selection. What did invert poses was the `approach_sign` polarity bug
+recorded above; the residual could not see it, and neither could that up test. See
+`inverse-kinematics.md` → *the face is aimed at +Z* and *the two exact poses of one
+normal*.
 
 ## What was wrong before, and why it is worth recording