fix: enforce b-spline displacement constraints

ClumsyPilot/tests/verify_path_smoothing_bspline.ps1

@@ -77,9 +77,13 @@ function New-AlgorithmInput([object[]]$Segments, [double]$ReserveMeters) {
     return $inputConstructor.Invoke(@($preparedPath, (New-EmptyMap), $vehicle, [double]0.05, $ReserveMeters))
 }
 
-function Invoke-Smoothing([object[]]$Segments, [double]$ReserveMeters, [double]$Strength = 1.0) {
-    $candidate = $smoothMethod.Invoke($smoother, @(
+function Invoke-Candidate([object[]]$Segments, [double]$ReserveMeters, [double]$Strength = 1.0) {
+    return $smoothMethod.Invoke($smoother, @(
         (New-AlgorithmInput $Segments $ReserveMeters), $Strength, [Threading.CancellationToken]::None))
+}
+
+function Invoke-Smoothing([object[]]$Segments, [double]$ReserveMeters, [double]$Strength = 1.0) {
+    $candidate = Invoke-Candidate $Segments $ReserveMeters $Strength
     Assert-True (Get-PropertyValue $candidate 'Succeeded') 'B-spline smoothing must produce a candidate for the deterministic fixture.'
     return @(Get-PropertyValue $candidate 'Segments')
 }
@@ -198,6 +202,26 @@ foreach ($point in $cornerPoints) {
     Assert-True ((Get-DistanceToPolyline $point $cornerSource) -le ($allowedRadius + 0.000000001)) 'Every B-spline displacement must stay inside the per-anchor clearance reserve radius.'
 }
 
+# A tight reserve may not publish an evaluated B-spline that leaves its 0.005 m movement radius.
+$tightReserveCandidate = Invoke-Candidate @((New-DirectionSegment 0 $forward $cornerSource)) 0.075
+
+# A tight endpoint circle that cannot meet the heading=0.2 rad tangent ray must fail, not silently rotate the handle.
+$misalignedHeadingSource = @(
+    (New-Point 0.0 0.0 0.0 0.2 0.08),
+    (New-Point 0.05 0.0 0.05 0.0 0.08),
+    (New-Point 0.10 0.0 0.10 0.0 0.08),
+    (New-Point 0.10 0.05 0.15 ([Math]::PI / 2.0) 0.08),
+    (New-Point 0.10 0.10 0.20 ([Math]::PI / 2.0) 0.08))
+$misalignedHeadingCandidate = Invoke-Candidate @((New-DirectionSegment 0 $forward $misalignedHeadingSource)) 0.075
+$requiredFailures = New-Object System.Collections.Generic.List[string]
+if (Get-PropertyValue $tightReserveCandidate 'Succeeded') {
+    [void]$requiredFailures.Add('A tight reserve published an evaluated candidate outside its permitted movement radius.')
+}
+if (Get-PropertyValue $misalignedHeadingCandidate 'Succeeded') {
+    [void]$requiredFailures.Add('A tight reserve silently accepted an endpoint handle that cannot follow the supplied travel tangent.')
+}
+Assert-Equal 0 $requiredFailures.Count ([string]::Join(' ', $requiredFailures))
+
 # Adjacent direction segments retain their duplicated switch pose and independent topology; no fit may cross the switch.
 $reverseSource = @(
     (New-Point 0.10 0.10 0.0 ([Math]::PI / 2.0) 0.08 $true),