fix(physics): AD-66 relands — the push-out uses retail's bare radius; plant-then-lift complete (#341 closed)

Third attempt, landed on evidence where the first two correctly refused:
the ten-run stability gate passed 10/10 bit-identical (0x42667451, two
clean-room cycles among the runs), the recalibrated golden's every value
measured with derivations rather than guessed, and the historical
measurement flip stands recorded as unexplained-but-unreproducible
after 37 hunt runs plus these 10 found no divergence anywhere.

The mechanism, completing the S4b byte-pin: validate_walkable plants
the sphere at perpendicular r*N.z (byte-faithful, untouched); this push
fires once per settle and lifts to tangent equilibrium dist=r, where
the trigger goes quiet — retail's slope hover, arriving via the push
exactly as the original substitution's own comment predicted retail
had. Sabotage: restoring radius*N.z reddens the discriminating
exact-value test verbatim. AD-65 conformance, the uphill no-flap
guard, and the #331 absorb pin all green untouched.

AD-66 retired (the campaign's last withheld row); AD-69's seam-frame
correction deliberately unbundled, stays active as its own follow-up.
Clean-room suite 11,267 / 4 / 0 — the suite's two AD-66 skips are gone.

User's "port the retail pair" decision is now fully executed; the
hover-look slope gate is the remaining acceptance.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/AcDream.Core.Tests/Physics/S4AdjustOffsetConformanceTests.cs

@@ -123,7 +123,13 @@ public class S4AdjustOffsetConformanceTests
     /// zDist formula, not the radius*N.z one.</item>
     /// </list>
     /// </summary>
-    [Fact(Skip = "AD-66 WITHHELD 2026-08-07: retail's bare radius is byte-confirmed but the landing was pulled after the same clean-room binaries measured contradictory absorbed-tick behaviour flipping with test-assert shape alone. Unskip with the AD-66 relanding. See the S4 outcome note in the contract doc.")]
+    // AD-66 RELANDED 2026-08-08 (issue #341): the #341 boundary hunt ran 37
+    // measurements of the historical assert-shape flip across three JIT
+    // tiering configurations and found it unreproducible (37/37
+    // bit-identical). The reland's own ten-run gate on
+    // RuntimeRemoteUphillProgressTests.AnExactlyUpSlopeOffsetIsAbsorbedByThePersistedSlidingNormal
+    // also came back bit-identical across ten runs. Un-skipped.
+    [Fact]
     public void AdjustOffset_SafetyPush_UsesBareRadiusForTriggerAndNumerator()
     {
         const float radius = 0.5f;
@@ -172,7 +178,9 @@ public class S4AdjustOffsetConformanceTests
                         $"{(naturalRestingDistOld - dist) / normal.Z:F7} AND would not have fired at all.");
     }
 
-    [Fact(Skip = "AD-66 WITHHELD 2026-08-07: retail's bare radius is byte-confirmed but the landing was pulled after the same clean-room binaries measured contradictory absorbed-tick behaviour flipping with test-assert shape alone. Unskip with the AD-66 relanding. See the S4 outcome note in the contract doc.")]
+    // AD-66 RELANDED 2026-08-08 (issue #341): see the sibling test's comment
+    // above for the boundary-hunt evidence. Un-skipped.
+    [Fact]
     public void AdjustOffset_SafetyPush_DoesNotFire_WhenAboveBareRadiusThreshold()
     {
         const float radius = 0.5f;
@@ -194,10 +202,11 @@ public class S4AdjustOffsetConformanceTests
 
     // =========================================================================
     // Uphill no-flap guard. Written as the S4 contract's AD-66 STOP-condition
-    // scenario; AD-66 was then WITHHELD (issue #341), so this currently runs
-    // against the RETAINED radius*N.z substitution and its green is evidence
-    // about THAT code. It must stay green across the AD-66 relanding too —
-    // it is the scenario the substitution was originally written to protect.
+    // scenario. AD-66 relanded 2026-08-08 (issue #341's boundary hunt); this
+    // now runs against the bare-radius push and stays green under the
+    // plant-then-lift mechanism (the lift settles to tangent equilibrium on
+    // first contact and then goes quiet, so it does not re-fire every tick
+    // and does not flap OnWalkable running uphill).
     // =========================================================================
 
     /// <summary>
@@ -292,8 +301,9 @@ public class S4AdjustOffsetConformanceTests
                 $"tick {tick}: contact must not be lost running uphill (the AD-66 flap symptom)");
             Assert.True(result.OnWalkable,
                 $"tick {tick}: OnWalkable must not flap to false running uphill on a walkable " +
-                "slope. Written as the S4/AD-66 STOP condition; with AD-66 withheld (#341) it " +
-                "guards the RETAINED substitution and must survive the relanding.");
+                "slope. Written as the S4/AD-66 STOP condition; AD-66 relanded 2026-08-08 " +
+                "(#341's boundary hunt) and this guards the bare-radius push under the " +
+                "plant-then-lift mechanism.");
 
             position = result.Position;
         }